I World War !I 

Volume 5 

united states cryptologic history 

A Priceless Advantage: 

U.S. Navy Communications Intelligence and 

the Battles of Coral Sea, Midway, and the Aleutians 
This monograph is a product of the National hritg Agency &tory 

program, 14s contents and concldoms are those of the author, based 

on original march, and do not necessarily represent the official 

views of the Nadotld Security Agency, Please address divergent - op- or addihnal detail to the Center for Cryptologic &tory 

W photographs are &om the NSA Arehivesor US. Navgla& 

Cantem& of this gublIEatl0tl should not be raprodd or further disseminated outaide 

the U5.hWUgence Communl~witlmmt the -aftbe Director, NSA. InqPirh 

aboutregroduetronaad - should be directed to ths hkr for Cmtddc 

~iistwg,~~tti-~ kd~ AM, I~~G.~~MD%O~~~W 
ERRATA 

A PriceIessAdvantage: U.S. Navy Communications Intelligence and the Battles of 

Coral Sea, Midway, and the Aleutians 

p.15: In second paragraph, second line, first word should be "Huckins" not 

"Huggins." 

p. 26: Captions under the photos should read "Japanese Aircraft Carrier Hiryun and 

"Japanese Aircraft Carrier kryu," respectively. 

p. 56: Caption under photo should read "Japanese Aircraft Carrier Akagi." 
UNITED STATES CR YPTOLOGIC HISTOR Y 

Series IV 

World War II 

Volume 5 

A Priceless Advantage: 

U.S. Navy Communications Intelligence and 

the Battles of Coral Sea, Midway, and the Aleutians 

Frederick D. Parker 

CENTER FOR CRYFI?OLOGIC HISTORY 

NATIONAL SECUMTY AGENCY 

1993 
Table of Contents 

Foreword 

A Priceless Advantage: Intduction 

Part One: The Battle of the Coral Sea 

Part Two: The Battles for Midway and the Aleutians 

Bibliography 
Foreword 

This volume is the third in the Center for Cryphlogic History's series documenting 

United States communications intelligence in World War 11. The first volume was Dr. 

George F. Howe's Amrican Sigd Intelligeme in Northwest Africa and Western Empe, 

subsequently released to the National Archives and Records Administration as SRH 391. 

Frederick Parker's New View to Pearl Harbor followed; this was the fwst volume in a major 

project documenting US. Naval COMINT in the Pacific Theater in World War 11. 

As was the case in his earlier work, Mr. Parker has diligently researched and analyzed 

the surviving COMENT records held by PJSA, the military services, and the National 

Archives. The process of locating and identifying these World War 11 COMINT reoords has 

been, and continues to be, agonizingly slow. Contrary to the impression held by some 

outside historians, these documents are not neatly marked and arranged in drawers 

awaiting our use. 

But the time and effort have been extremely worthwhile. Mr. Parker has combined 

meticulous research and careful analysis &he COMINT and then has Mended the GOMINT 

history with the facts from published accounts of the military operations involved. 

The cryptologic profession has long been aware of the role played by ColrdINT in the 

Battles of Coral Sea and Midway and that Midway was a pivotal action in the naval war in 

the Pacifw. Mr. Parker has providd the reader, at last, with a masterfully detailed 

account of the COMINT associated not only with the Curd Sea and Midway actions but also 

with the events in the Aleutians, often neglected or given superfrcid treatment by some 

historians. And, as Mr. Parker documents, there is a very interesting story of the non-use 

of C~~NT by the commander of the U.S. task force. 

Beyond the treatment of the role of COMINT in the battles, however, Mr. Parker has 

provided the reader with a marvelous context from which to view the unfolding hishy of 

U.S. navd in the Pacsc. He has presentd the reader with a continuity often 

lacking in accounts of individual events or actions. The history of U.S. naval in 

World War II cannot be viewed simply as related to specific battles or events but as an 

evolving, dynamic, changing entity with a recognizable history of its own. Mr. Parker's 

works provide a continuing examination of the organization, personnel, policies, and 

operating prmxdwes of the sdl COMrrr organization of the 1930s as it desperately 

struggled to bth meet the exigencies of war plan for the future. Mr. Parker has provided 

the cryptologic profession, the academic community, and the public at large, with an 

exciting history. Future volumes are eagerly awaited. 

Mr. Parker has been a reemployed annuitant working in the Center for CryphIogic 

History. The Center lost all of its reemployed annuihnts late in 1992. Since that time, 

Mr. Parker has rejoined the Center as a cleared volunteer, and continues to make 

invaluable contributions to U.S. cOM~ history and to U.S. hisbry. 

Henry F. Schorreck 

NSA Historian 
A Priceless Advantage: 

U.S. Navy Communications Intelligence and the 

Battles of Coral Sea, Midway, and the Aleutians 

If 1 am told to fight regardless of the coneequences, I sW rn wild considerably for the firat six 

months or 8 par, but I have utkrly no canfidence for the second and third yeam. . . . Now that 

the situation come to thia pas% [the Tripadite Pact] I hope you will endeavor for avoidance of 

an America-Japanese war. ' 

Admird Imroku Yamamoh, 

Commmnder in Chief, Japanese Combined Fleck tu Prince Konoye. October 1940. 

Historians in Japan and the United States have already written much abut the 

period between 7 December 1941 and the Battle of Midway early in June 1942, a period 

when the United States was on the defensive in the PacXu: and US. policymakers were 

unsure how the war against Japan should be prosecuted. Using their histories as 

background, this study focuses on an obscure but important program, the U.S. Navy's 

cornmuniations intelligence (COMINT~ effort, which, despite its size and the trauma of 

Pearl Harbor, proved to be an unprecedented, sole, and timely source of information 

concerning Japanese intentions and strategy. 

The study chronicles how, by reorganizing and redirecting its resources, U.S. Navy 

communications analysts engineered a spectacular triumph over Japanese naval 

cryptography and how the reports produced by these analysts contribuM to development 

of a new U.S. naval strategy in the Pacific. By intercepting, deciphering, and translating 

the Japanese Navy's messages that contained their order of battle, the timetables for their 

military operations at Port Moresby, the Aleutians, and Midway, and a myriad of vital 

details concerning their most secret plans and intentions, the communications analysts 

were vindicated of any taint of failure from Pearl Harbor. 

Perhaps most importantly, this study provides an in-depth examination of what U.S. 

communications intelligence learned from Japanese Navy communications; how this 

information influenced U.S. Navy decision makers in Washington and Hawaii, who 

developed an American strategy to stop the advancing Japanese; how completely it 

frustrated Japanese strategy in the second phase of the war; and how it affected the 

outcome of two historic sea battles. In the words of Admiral Chester W. Nimitz, COMINT 

was entitled to a "major share of the credit for the victory at Midway." 

The study also marks the appearance of radio intelligence detachments and linguists 

aboard ship. Although not the first time the idea of intercepting enemy naval 

communications from a floating platform had been attempted, the Battle of the Coral Sea 

marked the Grst time it had been tried by the U.S. Navy under actual wartime conditions. 

Evidence indicates that the contribution of this experiment to the wnduct of the tactical 

war was imporhnt, even vital, and vindicated the wisdom of the earlier experiments. 
Because it was new and secret, however, it may have depended to an uz1workable degree 

qn the relatiomhip between the individual detachment and the task force commander. 

With the buildup of khe Australia-New Zealand Forcea (ANZAC) command in January 

and February 1942, the relocation of General Douglas MaeArthw to Australia in midMarch 1942, and the creation of the Southwest Pdc Theater on 30 March 1942, other 

forms of inblligence information -me available to U.S. policymakers, s~~, and 

tacticians. During the Battle of the Coral Sea, for example, comm+tiom intelligence 

and aerial photography formed an enviable -emhip in support of the A- task 

force mmmadem. Indisputably, however, at tbis stage of the Pa&c war, no other source 

of either strategic or kctical intelligence mdd compare with radio intelligence. It truly 

gave Admiral Ernest J. King, Commander in Chief, U.S. Fleet (COUCH) and Admiral 

Chester W. Wimitz, Commander in Chief, Pdc Fleet (CINCFAC), a "priceless advantage" 

over the Japanese. 
Part One: 

The Battle of the Coral Sea 

JAPANESE STRATEGY 

Japan started the war in Asia and in the Pacific to establish and protect a "New Ordern 

in Ask2 In "Phase I" of the war, the "operational objective" of the Imperial Fleet, in the 

words of Combined Fleet Secret Order Number One, issued on 1 November 1941, was 

expressed as follows: ". . . by ejecting British and American strength from the Netherlands 

Indies and the Philippines, to establish a policy of autonomous self-sufficiency and 

economic independen~e."~ Willmott, in the same vein, asserts that 

. . .of all the major combatants Japsn alone did not aspire to a final victory.. . . Japan's goal was 

to secure a negotiated peace by limiting and winning the contlict she began . . . in 1941. She 

aimed to force her enemies to come to terms with the gains she intended to make in the opening 

months of the war.' 

Asia was defied by those Japanese who shared this vision of the immediate future as 

including India and Indonesia, as well as China, Manchuria, and all of Southeast Asia, 

including the Philippines. Australia was on the periphery of Asia, in danger of being 

swept into its definition at the next favorable turn of events. 

Phase I of the Japanese master plan for the conquest of this vast area actually ended in 

the central and western Pacific in March 1942, with the unexpectedly quick and easy 

defeat of Australian, British, Dutch, and American forces and the fall of Java. Heroic 

American naval, ground, and air forces on Corregidor did not capitulate until 6 May 1942. 

The fall of Java, however, marked the end of effective naval resistance in the entire region 

from Singapore to New Guinea. 

Flush with their uninterrupted string of victories, Japanese army and navy planners 

agreed, probably in late December 1941 or early January 1942, that the United States and 

Great Britain must be prevented from developing Australia as a base from which to launch 

a counteroffensive. How this ambitious goal was to be accomplished became a matter of 

contention, however, and a controversy developed between the army and navy over the 

"propriety* of actually invading Australia and India. The navy reasoned that, to keep the 

U.S. and Great Britain on the defensive, all Japanese military arms should be constantly 

on the offensive. Amrdingly, naval strategists recommended a far-reaching but vastly 

unpopular menu of joint armylnavy amphibious offensives throughout the central and 

western Pacific and in the Indii Ocean to be accomplished in the fist six months of 1942.5 

The navy wanted the army to invade India and Australia. Always mindful of its heavy 

troop commitments in China, Manchuria, and Southeast Asia, and never an enthusiastic 

supporter of naval strategy, the army managed to convince the navy that the strategy was 
beyond its apabilitiss. Instead, it agreed to a policy also conceived in the navy, but much 

more economical of army resources, to help the navy sever communications between the 

U.S. and Australia and the U.K. and India. If successful, such a policy would complete the 

kulakion of Australia, prevent an Anglo-American muntedensive in the P6c, reduce 

western aid to China, and place India, Australia, and New Zealand well within the sphere 

of Japanese influence without resorting to a serious expenditure of army remurces. Thus, 

the army and navy created out of this compromise the hit Japanese strategy of Phase I1 

of the war in Asia and the Pacific: to blab and neutralize Australia and India, rather 

than invade them.' The Japanese Navy lost no time in implementing this policy. 

Coral Sea 

The Cord Sea aad Surrounding Area 

On 23 January 1942, six days after their successful operation against the city of 

Waul on the island of New Britain, Japanese Imperial Headquarters published Naval 

Mve #47, which immediately became the basic architecture for their Phase I1 

strategy. It ordered the army and navy to cooperate in seizing the ports of Lae and 

Salamaua on the northeast coast of Papmew Guinea.7 After these operations had been 

compleki, the navy alone was to seize Tulagi, an island near Guadalcanal in the 

Solomons. Following the occupation of Tdagi, the army and navy were again to cooperate 

in seizing Port Moresby, an Australian base on th~ southeast mast of Papumew Guinea. 

After Moresby wa~ rsecurecl, the Japanese planned to launch their campaigns against New 

Caledonia, Fiji, and Samoa, all of which lie east of Australia, thus effectively emircling 

the northern half of eastern Australia and cutting off communications with her U.S. 

allies? 
In mid-February a "local agreement" was reached by the army and navy to implement 

Directive #47 in early March beginning with the joint effort to seize Port More~by.~ To 

effectively isolate India, the main base for western aid to China, and incidentally to protect 

the army's efforts in Burma, the Combined Fleet also planned unilaterally to continue 

strategic offensive operations and to inflict as much damage as possible on the British Far 

Eastern Fleet by simultmeously sending carrier strike forces to the Bay of Bengal and the 

Indian Ocean.'' Immediately after the Moresby operation, Directive #47 ordered the 

Fourth Fleet to seize Ocean and Nauru in the Gilberts. These lightly defended equatorial 

islands were part of the Trust Territory of the Pacific administered by the United States. 

Then the Combined Fleet would regroup at &bul and Truk to any out joint operations 

against New Caledonia, Fiji, and Samoa. " 

In the euphoria of their victories, the Japanese disregarded the possibility that any 

power or weapon could derail their intentions. However, thanks to the aggressive U.S. 

strategy of using carrier task forces in hit-and-run raids, the road to Japanese success in 

Phase TI was not to be as smooth and uninterrupted as in Phase I. Two episodes involving 

U.S. carrier aircraft convinced Admiral Shigeyoshi Inouye, Commander in Chief, Fourth 

Fleet (CINC 41, that control of the skies was not assured and that he needed carrier 

support to counter the unforeseen U.S. air mpability if he were to succeed with his planned 

invasion of Port Moresby.12 

AMERICAN COUNTERMMSWRES 

For the United States 1942 began with some extraordinary bad luck with respect to 

carrier strength. On 11 January 1942, Iess than two weeks after Admiral Chester W. 

Nimitz had assumed command of the Pacific Fleet, the carrier Saratoga was torpedoed by a 

Japanese submarine. Damage was so extensive that the vessel, only just arrived in the 

PMc, was returned to the West Coast for repairs. This temporary loss reduced the U.S. 

Pacific Fleet to three fast one-carrier task forces (TFs): TF 8, Enterprise, commanded by 

Captain George D. Murray; TF 11/16, Lexington, commanded by Rear Admiral Aubrey W. 

Fitch; and TF 17, Yorktown, commanded by Vice Admiral Frank Jack Fletcher. TF 17 first 

escorted reinforcements to Samoa and became available for offensive operations only on 23 

January 1942, the same day Rabaul fell to the Japanese.ls 

Regardless of the Paat Fleet's reduced circumstances, however, Admiral Ernest J. 

King, Commander in Chief, U.S. Fleet (COMINCH), insisted on a more aggressive plan of 

attack during the early months of 1942." From the intelligence reports provided by the 

Pac radio intelligence (RI) centers, he was confident of the success of the proposed hitand-run ventures. He knew that the Japanese had weakened their defenses in the central 

Pdc by transfers of land-based aircraft from the Mandates to the southwest Pacific, and 

he knew in detail the whereabouts and often the destinations of each element of the 

Japanese Combii Fleet. 
On 1 February 1942, Admiral Nimib dispatched two one-carrier task farces, 

E-rprise (TF 8) and Yorktuwn CTF 171, to conduct raids on Japanese-held islands west of 

Hawaii. The E-rprise operated against the Marsblls, Wake, and Marcus Islands until 

joining the Hornet, commanded by Captain Marc A. Mitscher, out of San Francisco, for the 

raid on Tokyo in April. The Yorhdown also attacked the Marshalls in early February but 

then saw little action until early March.I5 During those early months of 1942, the U.S. 

Navy also accomplished a major feat in establishing and maintaining air superiority using 

4er aircraft over a small but critical area in the northern Coral Sea. 

In mid-February Admiral King temporarily transferred the Lezingbon to Admiral 

Herbert F. hary, head of ANZAC naval forces with headquarters in Australia. Admiral 

Leaxy planned with Admiral Wilson Brown, commander of the task force, to send the 

kington immediately against the Japanese base at Rabaul. This plan was put into 

action, but on 20 February TF 11 was discovered before it mdd deliver its attack. For 

several hours that day the kington participated in the first battle of the young war 

between American fighter and Japanese bmber ahraft about 300 miles east of Rabaul. 

It was a signal American vicy. Though a minor skirmish by later standards, it 

seriously disrupted the balance of air power in the region. The Lezington lost only two 

planes and one pilot while the Japanese lost at least eighteen planes and pilots. The TF 11 

engagement, not decisive in itself, innicted serious losses in aircraft and pilots at a rate 

that Japan could not possibly suatain. la 

Despite the success of TF 11, it was clear that the U.S. and its allies were not seriously 

impeding the Japanese war machine in the southwest Pacific. By 9 March 1942, when 

MacArthur was completing arrangements to leave Corregidor, the Japanese controlled the 

Netherlands East Indies and virhally the entire north coast af Papdew Guinea. On 8 

March, Lae and SaIamaua fell to the Japanese, and Rabaui-based aircraft were poised h 

strike at Port Moresby on the south coast of Papua and Finschafen on the north coast near 

he. These strong points were the last signscant obstacles to complete Japanese 

domination of the world's second largest island. Unknown to the Japanese, however, 

another event involving a U.S. camkr task force was about to cause a major convulsion in 

their plans. 

After the aborted raid on RabauI, Admiral Leary returned the Lexington to CINCPAC 

control. On 10 March 1942, while the Japanese were savoring their vidries at Lae and 

Mamaua and were preoccupied with seizing the nearby port of Finschafen, the Lexington 

and the Yorktown, now constituting a new TF 11, lay unde- off Port Moresby . The 

task force launched its planes against the Japanese forces at Lae and Salamaua, attacking 

through a 7,500-foot pass in the 15,000-foot Owen Stanley Mountains, guided to their 

destination by a single mier plane, which orbited over the pass until the attack was 

completed. Compared to the engagement with land-based bombers off Rabaul on 20 

February, the American air raid on 10 March did little actd military damage." But it 

once again demonstrated to Admiral Inouye that he probably did not enjoy the necessary 

control of the skies required for the planned atbcks on Fort Moresby and Tulagi. 
The ontginal dam plan called for au amphibious &t on Momby, Opera& 

MO, in March 1942 to be supported only by land-- bombers ftom Rabaul aad 

seapb from newly cmdructd kms, ie., he, Sdamaua ad Fimcbfe~~ With the 

fea&li& d this plan in jeopardy hnse of the pressnce of an effective U.S. & fm, 

Admiral Inouye sought to postpone the indon of Moresby. He to his supwior, 

Admiral Isoroh Yamamto, Commander in Cbief, Combined Fleet, with a request for 

carrier support to emwe Japmw air 5uperiority befom prooesding with the invasion of 

Mod y. 

Admid Y-to agreed with Ad- Iaouye's -nt and allowed him to 

-ne -tion MO until May." Yamamoto also agreed to provide the carrier Kcrga 

from Carrier Division ICarDiv) 1" supplemented by r mtly m&Bioned light her, 

the Sbb, which was not yet assigned to a The Kagu, however, was reprted 

torpdoed on 17 March in the Lombok Straits.% This development led to the substitution 

of CarDiv 5's two -, Sb- a& ZM, bo the Fourth Weet for h M two 

& d May." Thew changes serbdy dhmptd Ymmnmto's original timetable for 

Phase II. 
r-a 

Aircraft Carrier Shokaku 

-a7 
Following the decision to po~tpne the invasion of Moresby, TuIagi, h, and Nauru 

Islands until a der force became available, Admiral Inouye deployed his foms in areas 

that were relatively secure from the threat of Ameb harasmmt. Using four heavy 

and two Iight muhem to aver three destroyers, two gunbats and the light dw Ch, 

CZNC4U*be~lOBdarChand19Aprilasfar~ardrrs~~ 

and constructed bssm on the north coast of New Guinea, impressively completing a 

defensive perimeter from the Solomons ta the Philippines.% 

On 23 April, Admiral Inouye issued South Seas Force Order #13 to rmme operations 

against Port Moresb. AnaIysb at Hyp, the radio intelligence center at Pearl Harbor, 

speculated that this order was actually delivered by pIane from CINC 4's Truk 

he-= rather than by radio communhti~ns.~ With the carriers and their escorts, 

the combined forces involvd reprewnted one of the largest collections of ships ever 

assembled by the Japanedle Navy.= The Comb'hd F'leek, meanwhile, inwead its aorta 

to build up pd ad air forces at Rabsul awl in the Mandates in mticipgtion of the 

larger F%ase II operations against Fiji% Samoa, and New Csledonia. The Shh and 

numerous cargo vessels wem used to ferry lad-based fighter and bomber aircraft from 

Japan through the Mandates to RabauJ while the airf~~lds on Timor, New Britain, and 

New Guinea continued to conduct air raids on Damin, Moresby, and bases and towns in 

the Solomofis, Many of these Japanese preparations for their numerous Phase II 

0pemtio11~ were dected in their naval communications and were detected by U.S. Navy 

communications monitors lmated at the radio intelligence centers in the Pacific Bash. 

NAVAL COllQNT CENTERS AND THEIll REPORIS ON JAPANESE PREPAIMTIOMS FQR TKE INVASION 

OF PORTMORgSBY,m,SAYOA,ANDNEwC~HU 

What tinu is it? Aomding to curred i&rnatbnal standard time ce, the region 

between -$ern Australia and Bougainville is in th Z + 10 or K time zone. At the 

beginning of bhs mr, burever, dl U.S. clwh mre set on War Time (+l hour). This 

dns why, MHpMdMeIbownemgesMdin*m&,&Wti~ inthis 

regionmtm&dusZ+11. Anmmsionoldiscreptq$w-apgwvsinth 

Yorktown intercept h?g kuse the ship dkd ~ and out of a + / - 30-dh tinu 

d*rence. 

May is the third month ofuutwnn in this region. According to Time Books World 

Weather GuiaEe, which Notional Gerrgrrrphic cmdtd at my request, &ylij~lir in &e Corcrl 

Seaat10~muthonl5ddqlr~lI hmrs,#m~,dat20&greessou&,I1 

hours 14 &&s. A* a fkw minutes for false &WR and auiilight ad a few minudes fot 

7-8 &ys'dflerence in dde when the &ys would be longer, uniialhwitg for the bt that ail 

the action d-y involving Admid Fletcher bkpke ut uppraimQteIy 15 &gre%a south, 

thuirolusofltioibi&on7und8Mqy1942 ggereprobbly MOOb1900kaltime. 

By the middle ofMarch 1942, two viable naval radio intelligence cenkrs existed in tbe 

Pacifzc: one in Melbourne, Australia, and one, Hypo, in Pearl Harbor, Hawaii. In response 
to the deteriorating situation on Corregidor, a possible threat against Hawaii, and the 

demand for informtion from everyone in &cia1 Washington, another center (Negat) was 

formed in Washington in February 1942 by the Communications Directorate using 

elements of OP-20-G. The center on Corregidor (Cast) was no longer affiliated with a fleet 

command, and its collection and processing capabilities were rapidly disintegrating as a 

result of evacuations of personnel to Australia and destruction of its facilities by bombing 

and gunfm. Prior to March, however, its contributions ta the rapid advances being made 

in naval cryptanalysis by the United States Navy were substantial. This was possible 

because, almost immediately after the war began, all the centers were Iinked by much 

improved communications, which made possible the rapid exchange of cryptographic 

information. 

OP-20-G Cdr. John R. Redrnan 

GA Cdr. Joseph N. Wenger 

GB Correspondence Howes 

GC Communications White 

GD Deception Smith 

GF DF Net-East Coast LCdr. Scott 

GI Combat Intelligence Sam Bertolet 

GL Collateral Information LCdr. A.W. Kramer 

GM Math Analysis Research Cdr. H.T. Engstrom 

GP Planning and Equipment Stanier 

GR Training and Personnel Hayes 

GS Machine Processing LCdr. H.O. Hogan 

GT Traffic Analysis Lt. R.I. F. Fravel 

GW Traffic Receiving LC&. W.F. Harringkun 

GX DF and Intercept Control LCdr. Welker 

GY Cr yptanalysis and Decryption LCdr. Parke 

GZ Translation and Code Recovery Kramer 

* Same Person 

OP-204 Washingtun (Negat) Organization, FebruaryJune 1943 

For some time, OP-20-G had used air mi1 for the transport of vital cryptographic 

material. In early January 1942, OP-20-G initiated a desperate attempt to speed up 

delivery of current cryptographic recoveries to each center. Washington authorized each 

center to send code and additive recoveries in radio messages on a special "COPEK" channel 

that linked Cast to Hypo and Washington and that by the end of March included 

Melbourne. The organization continued to use surface mail for the basic traffic.% Pearl 

Harbor and Melbourne shared the same Japanese Navy targets while Cast, for the 

remainder of its existence, reverted to priority support for the IocaI commanders. 

MeIbaurne from the outset, however, was a joint Austra1W.S. Navy effort supporting 

an international and unified command. Admiral Hart mandated this reIationship when 

the navy hastily moved Station Cast from the Philippines to Melbourne, Australia. 
The Station Cast contingent in Melbourne quickly evolved into the dominant partner. 

Tbis w& because of tZme central role played by the Amerian forces in the southwest 

PacEc as weU as the unique radio intelligence cupability represented by the Cast 

emmees. ~~t Rudolph Fabian, tka officer in dmrge (OTC), who had led the bt 

party "deployed~ hm Cormgidor, immediately e~tabliahed a ~011ectbn d pmcessing 

effort in Australia. U* almost exclusive1y his own resources, Fabian began to produce 

information concerning the Japanese fleet and its activities with particular emphasis on 

those elements of the Japanese fleet that threatened Allied naval forces in the southwest 

Prrcific, 

He ah provided daily briehgs for Admiral Herbert F. hmy and other senior U.S. 

Navy &ciala in the ANZAC fm MacArthur's hedquartem soon discovered his pmseme 

in Melbourne, and -1 ordered Fabian to include the Supreme Commander, 

Southwest Pacitic Area I~M~OWESPACFOR). Despite its obvious strategic and tactical 

value, there k ~hng evideme, to be introduced labr, that Wrthm, who was briefed in 

private, seldom used Fabjan's infbmmdn during this period ta support the naval task 

forces his aommsnd. (Moreover, the evihm that follows suggests that, when it 

was 4 it wss likely b to be) This pattern of daily M&ngs &ued until 

Madrthur's headquarters moved to Brisbane in the fall of 1942." Bec~use of the 

diippeamme of the organizational element known as the 18th Naval District and the 

subtitution of ANWC headquarters in its place, the situation in Hawaii regarding 

command relatiomhip and command intelligence interests was coqlebly diffemnt. 

GO Diplomatic and Nad AM Systems 

GX Trrtffic Intelligence Division (3 &cers, 4CRM) 

Japanese Weather Cwles 

DF Phttbg Center 

Tr&c Analysis 

GZ lkwmrch ad Exploitation of Codes (8 &rs, 3 men from Band) 

GY-1 Code and Cipher Idmetion d Key Recovery (JN 25) 

GY-2 Cryptanalysis ofJN 11 

GY-3 Cryptanalysis of JN 39,40,41,42,108,165,166,180,182,183, and 199 

GY-5 hsWns of all messages and muting of CI summaries, originator of 

cryp-- 
HAWMI (HY W) 

In Hawaii, the radio intelligence center known as Hypo was administratively 

subordinate to the 14th Naval District, just as Station Cast in the Philippines before the 

war had been subordinate to the 16th Naval District. Hypo was commanded by 

Commander Joseph J. &hefort, who was both a Japanese linguist and a cryptanalyst 

trained in OP-ZO-G by Laur~ce Safford and Agnes Drismll. Highly regarded by Word, 

Mefort at one paint was the head of OP-20-G while Sdord satisfied his obligatory 

period of sea duty. Wefort and Commander Edwin T. Layton, the intelligence officer for 

the Pdc Fleet, who was also a Safford-trained cryptanalyst, enjoyed an exceptional 

working relationship and a strong friendship. It had begun years before when they were 

both language students in Japan. Their offices were connected by a special telephone over 

which they conversed, often several times each day. 

Rear Admiral Edwin T. Layton Lieutenant Joseph John Rochefort 

Lacking such a dose working relationship with anyone in the 14th Naval District, 

which had no intelligence requirements to which it could conceivably respond, it was 

natural for Rochefort to consider CINCPAC as his command rather than the District. 

Slipping into this error was probably easy fox Rochefort because virtually aII of Hypo's 

resources were devoted directly or indirectly to satisfying intelligence requirements that 

originated with CINCPAC. Moreover, Bloch, who had preceded Kimrnel as CINCPAC, never 

required an accounting from Rochefort. 
- 

191&1925 Fleeah001 

1925-1929 OP-20-G 

1929-1932 Japanese Language Training 

1932-1933 ON1 

1933-1936 Fleet (USS Maryladl 

19361938 1 lth Naval District (ONI) 

1938-1939 Fleet (US$ New 0rEean.s) 

1939-1941 Fleet (USS Idi~~lislS~ 

Scouting Force WS PacSc Fleet) 

1941-2942 OIC Corn 14 RI Unit 

i 

JJ. Rochefort Tours of Dub, 191% 1&49 

Before 7 December 1941, intelligence requirements that cantrolled the collection, 

processing ancl reporting activities of the Hawaiian EU center were not stated in a formal 

manner by the Commander in Chief, P&XE Fleet. Hypo followed a simple collection and 

processing logic to the complete satisfaction of Layton and Admiral Kimmel. Its goal was 

to detect and report threats to the Pacific Fleet by monitoring the communications of the 

Japanese fleet. It gave priority to recovering communications of the Japanese Navy shore 

establishment, of major Japanese fleet units, especially battleships, cruisers, and mriers, 

and af those related to local developme&, particularly those involving submarines. From 

the surviving daily summaries from Corn 14 and the cINCPAC Intelligence Staff, it i~ elear 

that they were also concern4 with ground-based air units, particularly those deployed 

outside Japan. This latter concern did not arise entirely from the threat to U.S. 

possessions posed by the locations of the air units. The deployments of air units were also 

viewed as harbingers of offensive operations. 

Between July and December 1941, Hypo traffic analysts Lieutenant Thomas A. 

Huggins and Lieutenant John A. Williams, no doubt encouraged by Rochefort and Layton, 

had freely expressed their opinions and time after time, through Rochefort, issued 

warnings of Japanese intentions. It wag commonplace for them to assign a possible 

meaning or perspective to the patterns of fleet communications that might indicate 

concentrations of various elements, particularly if they threatened an important plaee or 

simply suggested hostile Japanese fleet intentions in general. The insights Rochefort and 

his analysts provided were usually forwarded to Admiral KimmeI unchanged by 

Commander Layton.= 

Following the Japanese attacks on Pearl Harbor and the Philippines, however, Hypo 

reporting hpd briefly into an eclipse that lasted until late January 1942. In sharp 

contrast to the incisive analytical reports that seldom left a Japanese initiative 

ut18munted for, probing beneath ship movemenks and patterns of oommunications 
activity, Hypo reports for weeks after 7 December 1941 were usually empty of any insight 

or interpretive comments. The daily reports continued to reflect comprehensive coverage 

of communications activity and fleet movements, but the bare facts were offered without 

any commentary whatever, leaving the reader to decide what it all meant. They aiso 

lacked something that had formerly been a hallmark of Hypo's analytic capability: a 

willingness to publish warnings whenever appropriate. One noteworthy example of this 

deficiency occurred in February 1942. Between 17 and 19 February, Hypo followed 

CarDivs 1 and 2, of the Pearl Harbor Strike Force, in the Netherlands East Indies, 

reporting their whereabouts each day. Layton's daily reports, perhaps lacking the insight 

formerly provided by the Hypo analysts, suggested that they represented a threat to Java 

and Timor. Sadly, this was not the complete story. On 19 February, without warning, 

planes from these carriers struck Darwin, Australia, in a devastating atta~k.~ 

Several reasons for the remarkable change in Hypo's approach to reporting on the 

activities of the Japanese Navy after 7 Dwember 1941 are suggested by the recollections of 

two of the principal figures in Headquarters CINCPAC and Hypo at this time: Admiral 

Edin T. Layton, intelligence &~er to both Kimmel and Nimitz, and Captain Thomas 

Dyer, cryptanalyst and Rochefort's second in command at Hypo. Layton suggested that an 

explanation lay in the new intelligence requirements mandated by Admiral Nimitz soon 

after he became Commander in Chief, Pacific Fleet, on 1 January 1942. Almost 

immediately after Nimitz replaced Admiral William Pye (Pye relieved Kimmel on 27 

December 19411, two circumstances combined to require a major change in intelligence 

priorities. One was the loss of Wake; the other was pressure from Admiral Ernest J. King, 

newly appointed Commander in Chief of the U.S. Navy. 

Admiral King believed he understood the intent behind the Japanese Navy's 

activities. Instead of continuing Admiral Pye's conservative defensive policies, King 

wanted the Pdc Fleet to conduct aggressive carrier raids on Japanese bases in the 

Gilberts and the Marshalls to check the Japanese advance and, most importantly, to 

reduce the growing threat to Samoa, Fiji, and the U.S.-Australian supply routes. His 

orders left no rm for Nimitz to pursue the cautious policies of his predece~sor.~~ King's 

attitude may well have influenced Nimitz to structure new and much more formal 

intelligence requirements than the informal understanding that prevailed before his 

arrival.31 

Much mare formal and specific than in the past, the new requirements called for 

information concerning "deployment of enemy carrier strike forcesfother carriers; 

disposition and strength of the Fourth and Sixth Fleets; deployments and strength of the 

twenty-four shore-based air forces, particularly the 24th Air Squadron known to be in the 

Marshalls; and enemy forces capable of furnishing significant reinforcements to the 

Marshalls/Crilberts by late January 1942."'~ Marked by the detachment of a commander 

who was unfamiliar with Hypo's capacity for analysis, the new requirements seemed to 
call simply for data on Japanese Navy capabilities - not warning, not insight into 

Japanesa intention& not even anal*. The new approach represented an immense 

departure hm the past and indieahd that the symbiotic relationship between Hypo and 

the Cmcp~c intelligence std had epded. It would be almost reassuring fo end the 

explanation here, but Captain Dyer offered another possible explanation for Hypo's 

ternporarp mewrphmis. 

CaptainDyer sggeaa that the unfortunate change in H~rp~'8 approach to reporting 

on the activities of the Japanese Navy was aused by 80~~ Ear lwrs -le: Hypo 

sdbred from a sense of guilt over what the world labeled as a spdaalar faiiwe of both 

intelligence and leadership." According to Dyer, all at Hypo who were dted with the 

catastrophe of 7 December 1941 vowed that guch a surprise would never happen again. 

Apparently they decided to let the faeta speak for thewlves. 

Though unlilrely to repmmnt a major #I= for the temporary dimintatinn of Hypo's 

genius, it was in faet litsrally weeks Wore the dytk talent at Hypo, whose output had 

shone so brightly in October d NO-& 1941, rmce again reclaimed its role ar a valued 

source of strategic intelligence to new commanders in the Patifie and Washington. 

Fortunately, the raheup dl for Ruchefirt and Layton to resume functioning as a team 

came stuttering b life in late January 1942, just as the Japanem Navy launched its Phase 

IIo~nsiv%~ Port Mohy. 

Rior to 7 December 1941,OP-20-G*s uh~~* supprt to the Chief of Naval 

Operatious, Admiral Harold R Stark, was vwy limited. It cmmhtd of support to the 

Atlantic direction ffnding (Dm net and the decryption and translation of Japanese 

diplomatic messages. By taking resources from OP-20-QY, the cryptanalysis 

organization, OP-20-G hitiakd a daily summary of information ht the Japanese Navy 

on 14 bmmk 1941. It waa M to gatis& the insatiable demand in Washington for 

wurent intew. It was an uma4i&cbry ~luth to tk ksk at hand because it 

eoptaind -nd-hand information taken from ths daily summaries hm Hypo and Castu 

In February 1942 OP-20-G completely reorganized, and its mission as a purely 

Pesearch Mty abrrrptly changd In the new structure, an analytic element called 

"Combat InteIligeme'' was cmaM aad ddgnabd OP-20-GI.85 Thb element pdud 

Little original current intelligerm until March, when intercept was obtained hm 

Cheltenham, Maryland, and murent deqpMmmIah on dN 25 (the Japanese Navy 

&nerd-Pu- Code) -s began to flow from OP-20-W and GZ, respectively. 

Tasked to ~~te the translatiom ta the 00~ and &id elements along with its 

own analytic reporb, OP-2041 became in effect a nominal 00m mtet in Wadngtm. 

UnN 15 May, bowever, it eonthud mainly h publish tmd&ka aad spdk reprts 
based on the output of Hawaii, Corregidor, and Melbourne. On that date the 

Communications Directorate authorized OP-20-GI to issue WCI summaries twice each 

day at 0600 and 1400, including traffic analysis (Cn reports prepared by the analysts in 

OP-~O-GT.~~ This development was imporhut in following Japanese preparations for the 

assault on Midway. Except for its substantial cryptanalytic contributions between 

December 1941 and May 1942, however, Negat was not a functioning COwm center on the 

order of Hawaii, Melbourne, and Corregidor when the Japanese began to implement their 

Phase I1 policies. Swcant functions such as traffic analysis and the production of 

reports based on the work of resident analysts were not developed in Washingtan until 

after the Battle of the Cord Sea. 

COMMUNICATIONS IM'EUIGENCE AND JAPANESE INTENTIONS TOWARD PORT MORESBY 

On 29 January 1942, the same day that Japanese Imperial Headquarters ordered 

Admiral Inouye to seize Port Moresby in early March, messages containing upper air 

observations for the region to the south began to emanate from Rabaul. In February 

Japanese land-based aircraft from Rabaul initiated bmbing attacks on the port, the town, 

and the nearby airfield. As each of these activities was detected by COMINT, U.S. Navy 

communications intelligence centers in Hawaii, Corregidor, and Melbourne seized the 

opportunity to issue warnings to King, Nimitz, and Hart. After the formation of ANZAC, 

Admiral Leary also received warnings of Japanese "future operations" in the direction of 

"Lae, Port Moresby, and the Solom~ns."~~ Collectively, the warnings led Layton (and 

Admiral Nimitzl to agree in late February that a Japanese offensive was planned for the 

Moresby area.= Within a week the task forces were also alerted. 

Initially excluded by the principle of need-to-know from distribution of 

communications intelligence, even that published by Layton, the carrier ak force KTF) 

commanders were added as soon as their forays began to produce a Japanese reaction. 

Individual intelligence items based on COMINT were supplied through C~NCPAC to his 

subordinates in a variety of intelligence media. From 1 to 16 March 1942, for example, a 

daily CINCPAC Combat Intelligence BulletinB based on COMINT supplied mainly from 

Hawaii, but with occasional contributions from Corregidor, was sent as a message to all 

CTFs. It was replaced on 17 March by the CINCPAC Intelligence Bulletin* that was also 

based on CoMINT with contributions from Melbourne and that, according to surviving 

records, was sent to the same distribution until 1 June, when it h ended temporarily. 

After the middle of March, all CINCPAC Bulletins that contained intelligence 

concerning the Japanese fleet were based principally on the following sources: individual 

messages translated by the centers and sent to CINCPAC; COMINT reports usually but not 

nwessarily based on translations that originated each day within Hypo:' the Corn 14 

Radio Diest that was usually sent onward by CINCPAC almost ~erbatirn;~' and the Corn 14 

COMINT Summary.49 After 20 March, when Melbourne began its daily reports, Hypo and 

CINCPAC cited the resuits of Melbourne's analysis whenever they appeared in their daily 

products. 
Aa an almost inflexible rule, the centem were not in direct contact with the 

task Grae commanders. Exceptions occurred only twice, both during the Battle of the 

Coralsea Thetwodvingmm=ges imd unique eo~tiona activity of 

the Jam strike forces. Though not vital jllfomation - the second message pwtained 

to activity that had med over nine hours More - these were the only two messages 

sent by Corn 14 to the task fame mmmander during the battlemu Even during a tactid 

&ah, Corn 14's rep& were ~nt only to CINCPAC and other corn and coma adhasees, 

ie, COmCH, COMSOwE3PM:, ad the other centers, via priority message% 

The swyiving CIMCPAC message file for the period between March and the end of May 

1942 suggests that Mackthur did not rely on Corn. It also meals that he too did not 

pwmit Fabian to 00mmunicat.e directly with the task force commanders. The messag~~ 

sent to the taslr force mmmaadets and to CINCPAC indicate that Madrkhur's preference 

was clearly slanted toward visual reconnaissance, including both aerial and coast watcher 

sources; he sel&m passed on to the CTFs any COMm learned from Fabian. The mme 

mcod also r%d that, after the BattIe of the Cod Sea, almost never appeared in 

the hm Madd~w's headq~.~ 

MacArthur's apparent reluctance &use communications intelligence may be due in 

part to an extraodhmy situation that developed with the first Corregidor contingent 

mn aRer Fabian arrived in Australia Far the i%t ten days between 20 and 30 Mad 

1942, ths OIC of the Melbwrne canter was not Fabian but Lieutenant Commander 

RdeM Mason, a Japanese linguist normally employed by the me of Naval Intelligence- 

(ON11 and formerly on the intelligence staff of the U.S. Asiatic Fleet. He probably 

QCCU@~ that @tion in the Melbourne center because of his rank, which was genior ta 

Fabian's, and LRary's mistaken notion of Mason's role in the detachment when he arrived 

in Australia via Java with the first party to be evacuated from Copregidor. At the end of 

the first report prepared by Fabian and his men, Mason appended the following comment, 

which revealed his distru~t of any C~WNT report not hased on a translation: 

k&odddwmyskhrmiamidtbatBIf sabjeettothermmbducedbyenemy~nat 

~~~~~rdopt,pndtothoPerewlting~tbeaaal~n'~~tiolrsof 

honest Mc. Hmca III, ~ooufid by CI or I)% bearinga, may give an entirely mihading 

pictureThis nob wa addressed Wemorandum for COIU[ANWCPOR," Admiral Leary, but 

bemm of the conhim over subordhation that briefly prevailed immediateIy aRer 17 

March 1942, when General MacArthur arrived in Australia, the note was probably 

intended for MWur as well. 

To mitigate the profwndly negative effecks such s comment would mdmbkdly have 

on any hegdquarhm receiving s-ent COMINT reports not based on translations, as 

well as on his own work force, Fabii appended a wcond note placing a more reassuring 

perspective on his men 4 their work: 
Note 52: Tbe information-gaining mpabilities of the unit are mmewhat re- at premnt 

but, while we are bringing our recod up to dmte, developing microfilm books, completing 

arrangements- for moving, collaboration, ete., we are scanning what traffic is available to us with 

phular straw on that addressed to or originated by units ansped of being ia the Bismarck 

Archipelago area and ah watching for he uniC on the DF 

By this statement Fabian, who was himself a cryptanalystP7 cleverly defended an 

American process of communications analysis probably keenly aware that for over twenty 

years his British counterparts had considered traffc analysis a "most valuable adjunct .ton 

and a "trustworthy substituten for cryptagraphy.'' Soon after these notes appeared, 

Lieutenant Fabian replaced Mason as OIC, and Mason dsparted for Washington, where he 

became head of OP-20-GZ Clhndationsl, a job usually held by a linguist appointed by 

ONI. dB 

It was a curious coincidence that this episode occurred just as the floodgates were 

abut to open allowing a torrent of Japanese Navy messages to be translated by U.S. Navy 

linguists at the PaeifIc centers. A major intelligence breakthrough for the United States 

occurred early in February 1942, when U.S. Navy cryptanalysts discovered that the 

change in the cipher for the Japanese Naval General-Purpose Code &IN 251 that murred 

on 4 December 1941, i.e., the introduction of cipher Baker 8, was in fact only a slight 

modification in the keying method employed in the Baker 7 cipher. To th consternation of 

the cryptanalysts at the time, however, the change from Baker 7 to Baker 8 frustrated a 

promising series of analytic successes against the ~ipher.~ Successful penetration of the 

new cipher in February 1942 meant that dl the work done since before Pearl Harbor on 

code recoveries and on the Baker 8 cipher could be applied to the JN 25 messages 

intercepted until the cipher changed again. Capitalizing on the breakthrough by 

increasing the numbers of key personnel working on the Baker 8 cipher and JN 25 code 

recoveries, the U.S. Navy, within a month, gained the ability to read all intercepted 

messages sent in this enciphered code. 

The increasing numbers of navy personnel assigned to the Pacific war effort in 

Washington and to the analytic centers in the Pacific slowly revealed ko the commanders 

of defending U.S. forces the Japanese Navy plans for offensive action from the Aleutians to 

Moresby." Af most everything written in radio intelligence reports based on message 

-c from mid-March to the end of May 1942 came from the one system, JN 25. By midApril, Japanese messages were being intercepted, decrypted, translated, reenciphered and 

disseminated by Hypo within six hours of their original transrnis~ion!~~ These reports 

would prove to be the most vital of the entire war.% 

With the advent of readable messages, -c analysts as well as cryptanalysts tapped 

a veritable cornucopia of Japanese Navy activities on which to report. Exuberantly, all of 

the centem routinely shared the full and often partially rewvered text ofdN 25 messages 
with the commands they supported. The practice of providing partid message texts lasted 

well into the fall of 1942% Although there is no indication that erroneous decisions were 

made based on partial message texts, this practice often left the task of extracting 

meaning from a partiaI translation to the commander's inteIligence staff.s5 

Notwithstanding this minor shortcoming, as will be seen in the following review of specific 

COMINT contributions to the decision-making processes of the headquarters served, all of 

the centers as well as the CINCPAC intelligence s- were prolific in producing CQMN 

reports that bore specifically on events occurring in the area between Japan and Australia 

during the period 15 March-May 1942. 

COMINT reports identified Rabaul with its concentrations of land bwcd bombcrs, Truk 

from which CINC 4 guided his surface raiders and submarines before moving ta Rabaul, 

and the flagship of Admiral Yamamoto, ClNC Combined Fleet, as the principal sources of 

much of the Japanese miwhief in the South PacXc. The centers also recorded a buildup of 

air, subsurface, and surface forces in the Fourth Fleet, while the attacks by bmhrs from 

Japanese bases in the Bismarcks and Solomons on northern and eastern Australian 

coastaI towns and Port Moresby continued with their attendant losses in Japanese aircraft 

and crews. 

The air buildup in the Mandates and in the Rabaul area reached the point in April 

1942 that Layton, affirming the view expressed in January by Admiral King, 

characterized it as a threat to U.S. supply lines to Australia. Adding possible substance to 

Layton's warning, Hypo on the same day reprted without comment that the Japanese 

navy minister, in one twenty-four-hour period, addressed no Iess than eleven dispakhes to 

Combined Air Force units in the Fourth Fleet area.s7 Although Hypo drew no concIusions 

of warlike intentions from the navy minister's activity, the center in Washington (Negat) 

saw part of the air buildup as indicating a likely Japanese offensive emanating from 

Rabaul and published a warning report to this effect.% 

In addition to the continuing weather reporting and bombing athcks in January and 

February, other revealing features to Japanese communications pointed unrnistakabIy 

toward Japanese fleet objectives. Perhaps the most prominent features were the 

diphigraph designator systems used throughout the Japanese fleet. The designators 

represented specific places throughout the Pacific and were often adapted to convey 

organizational information. The initial digraphltrigraph designators observed by navy 

COMINT analysts, though complex, were solved almost immediately. Digraphs beginning 

with A applied to American targets in the central and northern Pa~ific.~ Australian 

targets in the PapualSolomons region were assigned designators beginning with R, and 

those beginning with D were BritisWAustralian targets in the Indian Ocean (including 

Darwin - DP). From its initial discovery, COMINT analysts used this system as a basis for 

identifying Japanese Navy objectives. 

On 23 March 1942, for example, less than two weeks after the Pacific centers 

published their first translations, Corregidor published a report containing rtxoveries for 

eighty-nine designators, including AF for Midway and RZQ for Port Moresby." In early 

April the designator RZP appeared in a variety of contexts, which added to a growing 
reconnaissance patrols, of a like1 y Japanese attack. Unfortunately, one and possibly both 

of the messages came to the attention of a newspaper correspondent. The controversy 

generated by these disclosures did little to reduce Allied anxiety over possible Japanese 

suspicions that U.S. analysb were reading their most secret communication^.^ 

On 30 April, MacArthur received a message from General George C. Marshall, Chief 

of Staff, U.S. Army, concerning a story about Japanese intentions that had appeared in the 

Washmgbn papers under the dateline "Allied HQ Aust 27 Apr." The story revealed a 

"naval concentration . . . in [the] Marshalls, apparently preparing for [a] new opn 

[operation]." It was a very concerned General Marshall who pointed out that if the 

Japanese became aware of this story they would be "justSed in believing their codes 

broken - which would be disasterous [sic]." MatArthur denied any knowledge of a release 

conkining such information.@ Nevertheless, this incident may have contributed to 

MacArthur's negative attitude toward the use of COMINT in messages to subordinate 

commanders. 

Neither the Japanese nor apparently the PacXc centers ever became aware of the 

episode. Certainly nothing arising in the southwest Pacific interfered with the center's 

requirements to provide details of Japanese plans to attack Port Moresby. Several vital 

pieces of information, however, continued to elude the navy's analysts: when did the 

Japanese plan to attack; what forces were committed; and how many objectives were 

represented in the organization revealed in translations of 9 and 22 April 1942? 

The designators employed - MO, RZ, RX, RY - implied an operational concept 

transcending merely MO/RZ, the acknowledged designators for Moresby. Rochefort's 

people worked tirelessly to frnd spec& correlations and ease the level of anxiety in 

CIPTCPAC headquarters. Layton was particularly alarmed by he unknown elements of the 

Japanese plan and speculated that the impending offensive couId lead to a serious 

interruption in the flow of supplies to Australia and even to an attack on Australia itse1E7' 

This conclusion was stimulated in part by Hypo reports of the 22d and 23d, which for the 

first time detailed the strength of the Moresby operation. 

Hypo's reports were based on translations by Hypo and Negat of Japanese Navy 

messages intercepted between 19 and 22 April and on a report from Melbourne. Hypo's 

reports revealed that the MO Strike Force included Cruiser Division (CruDiv) 5, CarDiv 5, 

and possibIy submarines, and the light carrier Rydaku An equally alarming report 

on the 23d referred to the "powerful concentration" in the Truk area and erroneously 

included the carrier Kaga.= 
By 30 April 1942, after Admirals Khg and Nimitz had completed their first meethg 

in §an Francisco, none of the most vital issues was resolved, although the scope of the 

Japanese plan was now known. Translations and analytic effort identifled RXB as Tulagi 

and RY as an island in the Gilberts far to the east of Moresby. In addition, the names of 

Deboyne, Samari, and Cape Wey "Detachments" appeared in translations of Fourth 

Fleet messages, suggesting that these tocations in the Solomom Sea off the southern tip of 

Papua/New Guinea were included in the MU operation. A growing sense of urgency in 

Hawaii prompted Layton to publish a warning on the 30th that the Moresby operation 

"will begin very soon.yfi 

In a surprise move on 30 April, the Japanese fleet undertook to change their locator 

system. Their attempts -to conceal the new system failed completely, however, when 

~awaii intercepted a Fourth Fleet message containing both old and new designators. 

Hawaii hanslated a CINC 4 message to the Fourth Fleet, CruDiv 5, I lth Air Fleet, 4AAF, 

SUF, CarDiv 5, Kamikawa Maru, Ryhku I*], a destroyer division (DesDiv), an air 

tender, an air force at Rabaul, and others, indicating the "enemy" had discovered some or 

all of the reference point designators. Detailed changes in the system were mandated 

using the "Irohani Syllabari." The translation conveniently substituted digraphs for 

trigraphs throughout the operational area.74 

This development, which analysts saw as the final step before the beginning of 

Japanese operational activity, prompted Hypo ta publish an evaluation of the status of 

Japanese preparations. Their assessment of the forces gathered by the Japanese for their 

attack on Port Moresby was remarkably accurate. The MO, or Moresby, campaign was 

now under way. It encompassed southeast New Guinea and the Louisiades Archipelago. 

Australia was not an objective either at that time or in the follow-on operations to the east, 

preparations for which could not be clearly seen. The Aleutians were suggested, however, 

as a possible objective. The Japanese forces engaged in the campaign were listed: CarDiv 5 

and Crav 5, less the Nwhi (CA), with CruDiv 18 and Destroyer Squadron (DesRon) 6 

available. Also included were Gunboat Division 8 and New Britain Air (5A4F) consisting 

of Tainan Air, 4th Air Corps, and Yokohama Air. The Commander, CmDiv 5, Vice 

Admiral T. Takagi, was in command of the Strike Force, and ClNC 4, Admiral Inouye, was 

in overall command. At the time both were located in the Retbauf area. Light forces were 

said to be en route to the operatiom area. An unspecified number of air tenders and 

transports, one Submarine Squadron (SubRon) and the light carrier Ryhku [*I were also 

in~luded.~' Melbourne analysts disagreed with some portions of the Hypo translation, but 

both centers agreed on the fundamental point, that the MO operation was under way.7B 

(The MO-related forces consisted of almost 300 vessels of all types, including the following 

three CVs, nine CAs, fourteen DDs, eight SSs, and thirty-tbee warships of other types. 

Lundstrom says that the total number was 282.1 CIWCPAC'S estimate published in his OF 

Order listed a force considerably larger and significantly Merent from that published by 

Hypo but still far short of the actual strength. The discrepancy between Layton and 
Rochefort probably indicated the inelmian of unib Wort could not cob. Though 

sp&& types of vessels were bkd, CWCPAC did not attempt to correlate them with an 

Order of Battle: one BB from Battleship Divi~on (BatfXv) 3, three CAs, three aimaft 

ferries, and pwta of four CruDivs (4, 5, 0, and 18), skhn Dm, and twelve SSs." 

Altugethw the actual task force represented the largest yet assembled anywhere in the 

P&."l 

In addition to intramural disagreements, during 15 May analysts at all three eenbrs ... were metmud by mnwrive Japanese cornmupications security measures introduced 

throughout the CombM Fleet Fn the Fourth Fleet the we of tactical dlsigni by ship, 

a change of all shore station callsigns, the use of hlse dhigns by ships in the Moresby 

invasion forces, and a marked hmease in the volume of high precedence eommuuhtions 

complicated temporarily the task of identifying the fleet's communications 

hfkstmcture." Hypo was pmbabIy not done among the centma in admitting to "some 

confusionn caused by the aommuniations deception plans intrduced on 4 May into those 

elements of the Combined Fleet ahdy pmparhg for their Midway -tion. The most 

deceptive part of the plan was implemented by the Fifth Fleet on 3 May to cover the 

drawdowns on forces in home watera &tatd by the Moresby and Midway bui3dups. 

Such enforced p%movais 1& eqmd the astern appmacb to Japan. New callsigns were 

introduced in a special camrnukations drill intended h give the appearance of large 

force where none actually exMd80 

In Strike Force-related communkatiom, Japanese communications security measures 

may also explain what Melbourne inhrceptd on 4 May concerning the agpamm of the 

Kaga (CarIXv 11, CarDiv 2, Hiyu, Soyu, and elementg of BatDiv 3 and CruDiv 8 at Truk 

in an anchorage assignment message. No dates for the arrivals were given, but a second 

hamlation from Melbourne seemed b reinforce the likelihod of the Kqtp appearing at 

Ruk when "her mphm had been ~rnplebd.~' There are a number of explmations for the 

rnmmges conceraing the Kugq CarDiv 2, ek., appearing at this time. Whatever might 

have been the real reason for the messages, they added momentarily to the confusion by 

rekindling the mistaken idea among U.S. analysts that this activity was in some way 

related to the Moresby operation. 

The dapanese security measures &ected American uyptanalysh and Wc dysh 

and slowed the development of two major discoveries: the role of the Strike Force in the 

invasion and the impact on Xday uf bad weather delaying the progress of the Strike Force 

from Truk to the Coral k On 2 May 1942, both Hawaii and Melbourne inkcepkd one 

and possiily ho messages for the Strike Force detailing this information and much more. 

One message concerned the deliwry dder ahr& to Rabad by CarDiv 5 and ttte fact 

that bad weather was interfering with flight operations. The resulting delays caused a 

pstponenrent of the Strike Force's schedule until 8 May (7 May on the U.S. calendar).* 

On 3 May, Melbourne cryptanalysts noted that a possible second message to the 

dm implied that the Strike Force planned fo pass &northeast of Bougahville 

&re ib aimraft bombed TulWvm The same message, according to Hypo, odd the 

Strike Force to bomb Moresby on X-2 and X-3. Bawd on these messages, Hypo concluded 
Japanese Warship hyu 

that X-Day was 10 May. It was not until the Gfth, however, afkr much activity between 

Hypo and the other two centers in technical channels, that these translations were finally 

resolved and CINCPAC was able to advise the task forces of Japanese intentions: 

CINCPAC 0503292 to CTFlB and lE dap Commander Moresby Striking Force ~ComCdv5) 

indimtes 4 May that if Blue Stnking Fom is determined in Coral Sea (queptionable lacah) 

Orange SMcing force will proceed North North East of BougainviZle thence to southward. At 

0800 Item 5 May after arrival unknown place will proceed accordance further ordam. If m 

further ordm will go to Tulagi. If plane search in muthern and another sector needed Carrier 

Div 5 to ssnd his bombers to Tulagi at 

CIWCPAC 0503452 to CTF16 and 17: Reliable indicahm of 3 May: Orange Momby Striking 

Force cornpod of Crudiv5 and Cardiv5 will lad attacks on Allied barn Port Moresby areaon 

by miam 3 or Xray mhas 2 days. Attach b be launched from Sautheast (fmrly good but not 

certain). Xmy day not known but one indication pow to 10 May m Xray day. Above attacks to 

be carried out until rucce&aful completion by range.^ 
Meanwhile, BQacAdhr no- Admiral Fletcher cunmmhg the fm he was likely 

to enmuter at Momby. SpecSdly, throughout the day on 4 May MacArthur sent 

messages Burnmarking enemy actitity at Tulagi, $avo, and Guadabanal, and especially a 

report of an aircraft carrier and a possible battleship/cruiser in position west of 

Bougah*, all this iaformationwas baud on aerial rec~nnaissanee.~ Msssages had 

on aerial b umdly mve the ClFs the Zocations as well as the tm of 

Ja~~sighted. 

By 5 May, the centers were once again reporting on translations made the same day. 

Derived from Japanese messages on 5 May was the fact that an *Omuption Force" (a) was 

still in the Cod Sea*; Ib) would not be complete until joined by the Tuhgi Force at 1400 

on 6 May 1942; and (el would not laam the Coral Sea* More 1800 on the 7th when it 

*raoved south of Edm (*What was probably meant by the Japanese in inse 

mstmces was Solomom &a, the My of water between ~~ and Papdew 

Guinea, wbere the ships we- actually locatsd.) In addition, Gem1 MacArthur infd 

Admiral Fletcher and Admiral Nimita that reconnaissance aircraft from Australia 

reported sighting a Japanese carrier, s cruiser, and a tender in the western Solomons Sea. 

The locations given were west not east of Bougainvillea indicating the carrier was not part 

ofthe Sbike Force. 

hbdithut's headquarters also published a kadation supporting the strong 

prohbility that the carrier and its escorts were part of the "Occupation Force." The 5 May 

Japanese Navy massage gave a location for the Occupation Force that corresponded 

exactly with that of the carrier in the r~~oance reporb. Late on the fifth, in a rare 

departwe from normal practice, Mahthur's ha- sent Fletcher and Nimita a 

tmmlation fmm the Melbourne EU center that stated that at "0600 5 May the MO 

Occupation Forcen dl be in position "8 degmes north, 155 [degrees] blank minu- east 

$pd 23 course 300.- Moreover, COMNT revealed &at ship did not plan to leave 

the Solomom Sea until 7 May after they were joined by the Tulagi Force.' 

Melbourne also published translations concerning Japanese reconnaissance flights 

over the Cord Sea by 5AAF fighters d called attention to the use of Rabaul radio as a 

tackid headquarters by Admiral Inouye and possibly other ~rnders.~ Other 

~~ revealed the q of AM Inouyeas regarding the forces 

involved in Moresb and the entire region northeast of These items were not 

oonsidered imporbnt emugh by either Nimib or MacArthur to be forwarded to the task 

forces at that time. 

On 6 May Mdrthur's b ahdl filled the sky with activity over the 

vulnerable Japanese convoys awaiting the appearance of the Striking Force. The 

dapanese Zavashdhmpation, Covering, and upp port' Forces, ineluding the carrier 

Sbb, circled bheen Deboyne and bugahville, where they were repeatedly qwWd by 

American reconnabme aircdk and attacked by B17s from Moresby. None of this 

activity was reflected in the mmmmications of Japanese air patrols reportedly in the 
same area, suggesting that Japanese aviators were avoiding contact with the America 

pahl8.- 

Throughout the 5th and into the 6th M&ur repahdly sent Bl7s to bomb the 

da- collvoys. Each sighting and each attack was dutifully reported to the Am& 

task force commandem along with the location and makeup of each group of shipgB In khe 

message clispakhd at 0601452, MacArhur's headquarters also nutified the tad force 

wmmanders that, from inkmmpkd aftw 22302 on the 5th he learned that the 

Japanwe had sighted a U.S. amkr ad uyisers "on coume 190 sped 2ka This message, 

which Wed a -1 reference pint ad was either highly kccurate or poorly 

-law, represented the bt indication that the Japanese knew where the 

American dm were located. 

As&mcameoa7~y,tbe~~taskfo~m~~kaewhmorethan 

their Jam munkrpark hut the plans and dkpsitions of the opposing forces. 

Through a combination of eomrnunbtium intelligence ad aed recodmnce, they 

knew that a sit& Japanese carrier and its em* had actua11y been mghted west of 

Bougajnvdle d that the Japanese convoys caftying troops for the invasion of Moresby 

and their pWve covering forces were also loitering in the Solomuns Sea west of 

Bougainville. 

From commuuications intelligence alone they knew that the Japanese were devoting 

three carriers to the Moresby operation, the Shho, the Shokaku, and the Zuhku; the 

Invasion Force covered by the Shoho planned to enter the Coral Sea around the southern 

end of famew Guinea &r apturing the islands of Deboyne, Samarai, and other 

potential m~plane hmws in the Imisi&q the ho Strike Fome carriers of CarDiv 5, the 

SMar and the Zddu, were passing north-northeast af Bougainville pbubly ko enter 

the Coral Sea south of Wgi; the Strike Force intended to approach from the southeast 

sad bomb Moresby on X-3 and X-2; and that X-day was probably 10 May. 

The Battle of the Coral Sea began on X-3 day, 7 May 1942. At 0815 local time a 

Yorktown reconnaissance pilot informed Admiral Fletcher of two carriers and a Japanese 

task force at 10 degrees south, 152 degrees 27 minutes east This htion, where the 

Solomons Sea and the Cord Sea meet, was consistent with the reports from 

amunhtions intelligence and sighting reports from Mac#ukhur's aircraft. Because of 

improper encoding, the reconnaissance report was inconsistent with intelligence in 

identifying two carriers. A little over an hour later, Fletchsr launched a full air strike 

hm both the Ydtown and the Ldng#o~t against what he had every mason to believe 

was the SIcotco esoorthg the &rdy &cupation Force leaving the Solmmns Sea At 

approximately 1136 lod time, Admiral Flekher was undoubtedly gram to mive that 

brief but famnm message from Lieutenant Commander R. E. Dixon, a dive-bomber 

squadron commander from the kingtan: "Scratch one Flattop." 
During the next few hours Admirals Fletcher and Fitch received the bulk of their 

corn support from radio inter- detachments placed M their ders by Hypo.D6 

Admiral Pitch was also supporkd by a detachment in which the b@t was the late 

Admiral~nFutl8n~,whol&no~of~experiencesdatiag~bto& 

evenb. The Yorh detachment closely monitored the aorta of CarDiv 5 to recover 

ahraft fm the der Shho. They followed clmly the Japanese Strike Force's attack 

against the oiler Neosh and its emrt the destroyer Simm. The ling& has reported 

that he used Corn to influence Admiral Fletcher not b risk discovery of his task force by 

breaking radio silence to either wsm or reall the two ve~sels.~ CTF 18 was a 

~erabl~ fighting farce quite able to Mend itself. There may be another explanation 

for this dubious decision. 

At 1749 local time, the Yorktown's radar detected approaching enemy aircraft abut 

twenty-five miles away- Fletcher hunched 6ghter protection immediately, and the 

Amerhn aimaft quickly hound the appmdiq Japanese. Abut thirty mixlutes later 

the Japaneee abandoned dl radio hty, and the detachment repmtd to Fletcher a 

message to Commander, CarDiv 5, that *his attack squadron has been annihilated by 

enemy iightsr~.'~ 

3ehe.dawn on 8 May, Hypo provided CTJ!s 16 and 17 the new callsigns, hquendes, 

and procedures being used by the Japanese Strike Force and gave a new lmtion for the 

Japanese carriers. They were then laated only slightly to the northeast of the Amerhn 

task f~rces.~ Within three hours of receiving the message, Admiral Fletcher's planes, 

searching to the east as directed, found the enemy carriers. Shortly dktrward Admiral 

R& radioed both Nimih ad Madrkhur that a J-se naval force consWug of 

WV, 4CA and many DDA was located at "Lat 12 hng 1W" Flekher gave hls own 

position as "ILat11430 hng 154-30.- 

The attack on the Yorktourn and the Lexington lasted a little less than an hour and a 

half, from 11 13 to 1240 local time. Immdia~ly hr the attack, as happened the day 

before, the Jam pilots d radio operators aM the curriers "opened up their 

dm" and dkmW dty considerations. It was apparent immediately that 

something had happened b the SWu when it Failed to respond to dIs from its aircraft 

and the Zuikaku began seading homing signale and movering the Shhku's planes. The 

intercept operatom ehd the Yorkfown listened to these efforts and reported throughout 

the aRwnoon and evening that many aid were lost at sea or landed on isolated island 

beaches. After the Ywhm air groups completed tbeir attacks, intercept dvmed for 

Fletcher the damage reporb he wm receiving hm his At 1237 1-1 time 

Flebher notified Nirnitz d MacArthur that he had damaged an enemy carrier with two 

1,000-pound bombs and two torpedo hitsmLO' He also reported that his own force had 

sustained some -.'Og This message was probably welcome in Hawaii since a few 

miautes earlier the Melbourne center had sent them a message incbting a US. carrier 

had been sunk. A message horn the Z&u intercepted by Hypo at abwt the same time 

contained even more ominous news, It said that one U.S. carrier had been sunk and 

another had sustained the sure direct hit$,'@ Both centers combined to place CINCPAC in 
the remarkable psition of learning from Japanese sauroes the extent of damages tO his 

forces before he received the damage reports from his own hsk force commander. 

Fletcher 4 lnouye were apparently unable to assimilate and evaluate the unique 

ad vol~us ieports both undoubtedly received from COm d other sources about 

plane loeses and &er damag~ sushined by their enemy mberpart. Accordingly, e& 

chose slimilnr courses of action late in tbe afternoon of 8 May: d broke contact with the 

enemy ad retired from the scene. FIekher advised Nimita of his plans to retire overnight 

and "hll ~otktoron complekent planes as fhr aB possible from kington and send that ship 

to Pearl." lW Sen~ing that his intentions to retire might be mbundemtood, Fletcher also 

adW NMh and Mdur ahat "another enemy der has joined enemy foroe."lm 

Similarly, AM Inouye, aware of his own lo-, pwtkuhly in aircraR of all types 

and pilob, wdered the Strike Fame to break contack He ah postponed the attack on Port 

Moresby. Melbourne intercepted the wement order and reported it the same day.- 

Yamamoh abruptly rescinded Inouyds order to break conkct and ordered Admiral 

Takagi, Commander, CruDiv 5, to fd ruzd destroy the remaining U.S. fleet. In less than a 

full day, however, ttae search was dropped. Th&'tight Japanese schedule for post-Momby 

opsratbm took control ofevenb.'" 

The Battle of the Coral Sea was unique in U.S. naval annals and was the wne of 

many myptologic triumphs. To OP-20-G and the radio intelligence centers in Had, 

hm@dor, and Australia, the battle aad its prelimhxy qmdng afforded for the very 

W time the Wty to support three major shore-bad headquarters, Washington, 

Pearl Hubor, and Melburne, each vitally concerned with both the conduct and the 

outcome of a ma battle. By providing accurate d timely warnings of Japanese 

intentions beginning as early as January 1942, COMINT enabled Admiral King and 

Admid Nimih to psition mce U.S. Navy carrier task forces where they could intempt 

and Japanese plans and intentions. Moreover, after the Japanese Navy's 

General-Purpose Code {dN 25) kame readable in March 1942, COYKNT provided 

invaluable infmmation the Japanese timetable and order of battle for the 

invasion of Port Momby up to the very eve ofthe battle. 

The battle and its preliminaries were also unique to OP-20-G at the fighting echelons. 

S@al inhmeptfliqpbt detachments, the idea for which can be traced to the U.S. Asiatic 

Fleet's attempts to monitor Japanese communications during the Imperial Naval 

Emreha of the 1930s, were placed on board the aircraft carriers Bnteqwhe, kiwn, 

and Yorkbwn in early 1 942.LOs These detachments provided &tical support to the task 

fom commander during extended carrier sorties in the regions between Australia, Jam, 

and Hawaii. 

When in contact with the enemy, the detachment intercepted any HF communi~tions 

related to the action. On 7 and 8 May, in particular, the RI units provided an invaluable 
service to the commander afloat by following closely the communications between 

Japanese carriers and their aircraft. When not occupied with periods of actual fehting, 

they helped ta explain COWW-based reports sent to the task forces by their headquarters 

in Washington, Hawaii, and Melbourne. This vital service dosed a critical COMINT loop by 

linking the strategic system ashore and the tactical support system at sea. By all 

accounts, however, the detachmentlcomrnand relationship cannot be said to have 

functioned smoothly at this stage of the war. 

It is important to remember, however, that U.S. carriers observed a strict regimen of 

radio silence until located by the opposing force. This policy precluded pre-host iiities 

information of any kind passing from the task force to either CINCPAC or COMSOWESPAC 

headquarters. With minor exceptions, therefore, even after the Japanese discovered the 

American carriers, the commands ashore did not benefit from the local knowldge of the 

task force commander.lDg 

There is no indication that LU units afloat prepared any reports for consumption 

beyond the limits of their resmve flag plots. This conclusion is reinforced by the fact 

that reports from the shore-based centers did not contain details of the battle revealed by 

the RI units. Where there was duplication, it was clearly based on independent intercept, 

such as ship-bshore communications or sighting reports sent by Japanese aircraft or 

relayed by Japanese ground stations that were heard by both the detachment(s1 and 

Bypm'MelImurne. Et is also clear that, if the shore-based centers were to support their 

respedive commands with dekils of a battle in progress, further refinements of the 

instructions to the RI units afloat were required. The time remaining before the next 

crisis, however, did not permit the system to develop any corrective measures. 

Immediately after the battle, Admiral King accused Admiral Fletcher of an "apparent 

lack of aggressive tactics," i.e., his failure to launch night attacks. This criticism was 

echoed by Biard, when he described Admiral Fletcher as confused about Japanese 

intentions and disp~sitions.~'~ Both Nimitz and John Lundstrom, author of The First 

South Pacific Campaign: Pacific Fleet Strategy December 1941Jum 1942, placed part of 

the blame on communications intelligence. Lundstrom specifically noted in an April 1983 

article in Cryptalogia that conarm failed Admiral Fletcher, who, as a result, "piaced his 

Task Force 17 in jeopardy" on the morning of 6 May 1942. 

In his letter to Admiral King, Admiral Nimitz excused Fletcher's "long delay and 

apparent lack of aggressive tactics." He said that these failings "can be charged to the lack 

of sufficiently reliable combat intelligence."111 If this was a criticism of Biard, it was 

probably unwarranted, His after-the-fact log indicated that the Japanese radios were 

copied as smn as they broke radio silence the morning of 7 May. Biard, according to his 

account, was also aware that Hawaii and Melbourne sent Fletcher regular intelligence 

advisories prior to the battle. His monograph, while discussing in critical terms the 

disposition of Admiral Grace's task force of Australian and American war ships, actually 

indicated that on 7 May 1942 Fletcher had in fact directed his search aircraft east of the 

Luuisiades where COMINT had foretold, and aerial reconnaissance had already located, 
Japanese transports, a carrier, and other warships that represented a threat to Crace. (In 

Biard's article in Cryptdog, Admiral Crace's name is consistently misspelled.) 

With reference to the situation summary for 6 May, outlined above, it is dmdt to 

imagine what more the combat intelligence centers might have contributed concerning the 

Japanese forces prior to the engagement. Though Lundstrom was unaware of its 

existence, Biard's log indicates that the RI detachments were most supportive of Admiral 

FIetcher during the two days of actual fqhting. In the context of the total intelligence 

picture available to Admiral Fletcher, there may never be another situation in which a 

single source of information proves more supportive. Moreover, it is equally ~icult to 

imagine a situation in which two intelligence sources proved more complementary than 

COMINT and aerial reconnaissance were on 5 and 6 May 1942. 

THE LAND ROUTE TO PORT MORESBY 

The Japanese stubbornly refused to concede that this attempt on Moresby would be 

their last, Between 9 and 19 May, the Japanese continued to manifest an interest in 

reopening the original Moresby scenario. On the 19th, in fact, Layton reported that 15 

June had again been indicated as the date of resumption. On the same day Melhurne 

published a message from Tokyo Naval Intelligence, dated 18 May 1942, which, though 

unremarked by the other centers, acknowledged that "enemy" aircraft could now prevent 

Japanese resupply of Moresby (once taken) and proposed construction of a land route from 

Lae. 

The feasibility of the idea was recommended for study, and for nine days Melbourne 

continued to publish translations on this subject. On 27 May, in fact, a message dated the 

23d was published containing a detailed route across the Owen Stanley Mountains 

proposed by the 8th Base Force, Rabaul. This message referred to "General Staff Serial 

507," suggesting very high-level Japanese interest in the idea of a land route possibly to 

both capture and resupply Port Moresby.'12 Such ideas die hard, especially when they gain 

the favor of high-level pIanning staffs, but immediately after the Battle of the Coral Sea, 

other plans dominated the affairs of the Japanese Army and Navy. 
2. Hattori T&mhk, Tho Complete Histdry of the G-r East Asia War, Masu Publishma Co.. 1953. Voi. IX. 101. 

HereaRer Hattoti. 

3. morn a translation of this order found in the King papem at th Navy Historid Center and generously called 

to my attention by a fef low -archer, Captain Allen Bath, USN (r~tt). 

4. H.P. Willrnott, The Barrier and tho Yawlin, Annapolis, M mylard Naval Instikrta Prq 1983,3. Here 

Willmott. 

6. Hattori, Vol. II,Part 1,100-01,114-15,and 123. 

7. It was from the airfield at he that Amelia Earhart began the last and fateful leg of her around-the-world 

flight in 1937. 

8. This descripbon of Japanese plans is bamd on tbe following Hattori; Fuehida Mibuo and Okumiya 

Matake, Midmy, Tk &#le that Dmmsddapn, Annapolis, Maryland: US. Naval Inatitub. 1955. HereaRer 

Fuchida; John 13. Lidshm, Thu Sot& Pacifu Camprtign; ?'a&% Flaed Sbnfegy hmbm 1941Jutze 

1942, hpoh, MargW. Naval WMa Prees, 1956. Haredter Lunastom; and Samml Eliot Idorison. 

Hiato~ of US. Nami Opsrntiom in WWIX, hatan: Little, Brown and Co., f 971. Hereafter Morimn. 

Fuchida and Habbri describe a process ofmmpromisa beginning in January 1942 both within the navy and 

between the navy and the army that mud the Imperial General Staff's prewar policy of a atakgic defense to 

come under sttack. primarily by planners in the stalT of the Combined Fht. See Fnchida, 48-63, and Hattori, 

Vol. n, Part a, 100-49. Sea alao LunWm, 23-25 and 40-41, who fallows the Jam acconnta though not 

entirely from the same soureea. Morimn, VoI. U. 2, mted tbat a wtegy that relieved the army of any large-scale 

commitment of forces had actually been formulatsd in 1941 and published in Fleet Op Order #I, in November 

1941. This contention k not supportsd by the Combined Fleet trendation cited above or by Japanese munta 

13. Morison, Vol. 111,25940. 

14. See, for example, his mesaage of 2 January 1942 to CINCPAC that urged an "expedition of raid charachr 

against enemy baaea in Gilbert Ihds . . . . ' Blue Flag Memageq Reel TSL, Naval Histori-1 Center, 

Operational Archivea 

15. Morison, VoI.III, 269-64. 

16. Morison, VoL 111, 267; and Nimib Command Summary, 1041-1942 NSA History CoIlaction IV W 11.2.2. 

HereaRer Nimitz Command Summary. The Nimitz Command Summary for 25 February 1942 contained a 

Japanese memge to Bsrh that mentioned that "Japan will be unable to sustain losaa [in pild and airdl at 

their preaent rate." 

20. It waa the ShoWs fate to be known in COMINT by the wrong name throughoat it9 brief eristence. Called the 

Ryukaku as a red of c~ypbnalytic and translation errorb ita Arrect name was revealed by a WW in late 1942. 

HereaRer, whenever the incorrect name appear& itwill be followed by an asterisk!*). 

21. SRMNO12, Corn 14 TI Summaries with comments by CINCPAC Intelligence and Warplanes Sew RG457 

NA. To distinguish between the outpat of Corn 14 and CINCPAC Intelligence. I use the letter$ H for Corn 14 and 

UhJrton) for CINCPAC. SRMN012RI, 17 March 1942, repeated Corregidor's nnlocatsd report of th event. 

23. Morisbn, VoI. IV. 

24. See Corn 140203442 May 1942, in CINCPAC Message Fis.RG38.NA. 
26. Three grow were formed to implement the Directive: MO Striking Force. AdO hvhn Force, and Tulagi 

Invasion Force. South Seas Op Order # 13 ah wed "Cooperating Forc~'' in the form of 3m Air Forcse, and 

an AEF, (La, submarines in an Advanced Expeditionary Force), along with a timetable of eve&. The tirnekbl 

was as fouows: 

3 May, sek Tulagi and e&abhsh a seaplane base at Debope; 

4 May, invasion convoy depart Rabaul and land sin days later; 

10 May, seize Port Moreaby; 

15 May, capture Ocean and Nauru hlands. 

The ha1 metion of OP Order #13 gave a T/O (Table of Organization and Fuuctions): MO Striking Force (CarDiv 

5): The MO Skriking Force was to cover the Invasion Force, seek and my allied navd fom, attack died air 

bases in Ada and Moreaby; MO invasion Force: This force consisted of troopships, the SbAo, and four CAs: 

aad the Tuhgi Invasion Fom. The Tulagi force waa to break up and pin the MO and RY Forca &r Tdagi was 

aekd. Ludstrom, 68. RY meant Ocean and Naurk 

2%. History of OP-20-GYP, CMed Naval Archives, Crane Indiana. HereaRar History of OF-20-GYP. 

27. Fabian interview, NSA Oral History #09-83. 

28. SRMNO12, RE457, HA. 

29. Sea SRMN012fi-l and Lfor the period 17-1 9 February 1942. RW7, NA. 

30. See, for example, COMINCH memage 02171 82 January 1942, in Blue Flag mema. Reel +=I, Naval 

Historical Center, Operational Archive a 

3 1. bar Admiral Edwin T. Layton, with Captain Roger Pineau and John Coatello, And I Wm There. (New York 

Waam Morrow and Co., 19861,357. 

32. Ibid. 

33. Dyer lnterviear; U.S. Nan1 Institute, 224. 

34. Hi,+rg of OP-20-GI, NSA Hietary Cellectian, IVWI.5.3. Hareafter History dOP-2041. 

35. Bid 

36. IiistPry of QP-PO-GI; SRIi012, -7 NA. 

37. SRMN012(L)29 January 1942, RG457, NA. 

38. SRMN012 IL),RW?,NA, 25 February 1942. 

39. SRMHOOS, RG457, HA. 

40. S-004, RG457, NA. 

41. See,forexample, Bullatinsnumkr46 and 47,3001312April42 and0103112 May 1942,rsapectively. 

42. SRMNOOS. -7, NA. 

43. SRMNOIB, RW7, NA. Lagton, 37&79, identifies himself as the author of the BulZetit~~ and mentions some 

oftbamurcea 

44. See the Operational Riority messages from Corn 14 to CTF 16,0706302 and 0718522 May 1942 in the 

CINCPAC message jib, RG38, NA. 

46. Tbe record referr& to here is the CINCPAC rn-ge file. 

66. SRNSl617,ZO March 1942, Fleet Radio Unit Melbourne (7th Fleet) Daily Digest, 20 March 1942-30 October 

1944,FE457, NA. 

47. See NSA OH 09-83, Captain Rudolph T. Fabian, USN (ret). 

48. DennistPn papers, NSA History Collection. Although Deaniston used the word cryptngmphy, what ha meant 

was cry~nalysis. 

49. SKH 355, RG457, NA. HereaRer Holtwick. 

50. History of OP-20-GYP-1. 

51. Ibid. 

62. Layton, 376. 

53. Hiatoryofop-20-GYP-i. 

54. Dyer inbrview. 
!%. Aceording to the Clarke Papers in the HSA Histary Collection, the Britiah, finding it completely 

counterproductive, abandoned thia practice during the mid- to late Wea. 

56. Lawn. 

57. SRMN 012/H, RG457, NA, 2 April 1942. 

58. SRHOLZ, RW7 NA, 3 April 1942. 

59. One was- reported (AS), which analysts believed stood for San kancisoo. Corn 14 tu COMB 061 948Z May 1942, 

CINCPAC fde. 

60. SRNM012S/0126,23 March 194%. Misoehw ilrds pertaining to Japan- Naval Communications 

-1, -7, NA. 'HereaRer only the SFWN number and date will be given. ' ' ' 

61. CV,CarDivl. 

62. SRHO12,7 April 1942, SRNM0381,B April 1942, SRNS1517,Q April 1942. meet Radio Unit Melbourne (7th 

Fleet) Daily Digests 220 March 1942-31 OEtober 1944. Herear only the SRNS number and date will be given. 

All are RG457 NA. 

63. 3RNM091S, RG467 MA, 9 April 1942. This mesaage revealed the emncs of an MO Striking Force, ia., 

carriers; MO Mtack Force; RZP Occupation Force; RZP Support Force; RXB Occupation Force; and RY 

Occupation Force. RXB and RY were not immediately identified. 

64. SRMNOlZLRG.lli7NA,ll April 1942. 

65. D.M. Horner,"Special InkIligence in the Southwest Pacific Area in WIIn Australian Ohk Journal of the 

AJIA, December 1978, Vol. 32, No. 3; Willoughby Papem, U.S. Army Military Wry Inatituk, courtesy Dr. E. 

Drea. 

66. Ibid. 

67, The Iimits of MacArthtds air operations in early May were detailed in part one of a 15 May 1942 mewge 

from COMlNCH to CtEJCPAC, 142100-1421 182 May 1942. CINCPAC memage file, RG38, HA. 

68. Ibid. 

69. Bid. 

70. SRMN012n. RW7NA,23 April 1942. 

71. SRNM0609H, SRNS 1617, I9 April 1942; SRNMO613iN 20 April 1942 and SRMNOlZM. 22 April 194R all 

RW7 NA. 

72. SRNM 0659M, RW7 NA, 23 April 1942. 

73. SRNM0687,29 April 1942; SRHO12; SRNS 1517; CINCPAC Enemy Activitiee Fite. SRH 2721H; SRMNO11JL; 

all 30 April 1942 andallRG457NA. 

74. SRNMMl, 30April1942 RG457 NA. 

75. SRNM0713 andSRMNOl2,1Mayl942,RG457NA. 

76. SRNS 1517,l May 1942, RE467, NA. 

78. Morison, Vol. IV, 21-28: The Tulagi Invasion Force miled from Rabaul on 30 April 1942. WiIlmott: The 

Strike and Covering Forces sailed from Rdcon 1 May. Lundstrom: CINC 4 changed bi headquartera from Trult 

to &bad on 1 May 1942.). 

79. SRMNO12,30 April 1942 and 1 May l94RSRNS 1517,l May 1942, a11 RG467 NA 

80. SRHO12,3 May 1942.andSRMNOlWL.5 May 1942, RMS7 NA. 

81. SRNS 151 7,4 May 1942, RW7. NA. 

82. SRNM0911M,2 May 1942, RG457 NA. 

83. SRNS1517,4 May 1942, sndSRHOl2,3 May 1942,hth RG457 NA. 

84, CXNCPAC mesaage file. RG38, NA. See aLso SRHO12,3 May, and SRNS 15 17 4, May 1942; bth RGQS7, NA. 

86. ClNCPAC message Ale, RG38, NA See ah Belmnnen [Melbourne] 050150Z,aame file. 

86. In the CINCPAC message file, RG38, HA, see the following: 0402362, COMSOWESPACFOR to CTFs; 

0409502 COMSOWESPACFOB to all CTFs; 0410592 COMSOWESPACFOR to CTFs. 

87. SRKSl517,SRMNOIB, 5 May 1942.RG457,NA. 
88. COWWESPACEYIR to CTF 16, CTF 17, CINCPAC. etc. 0612002 May, CINCPAC Mmwage File, RG38, NA. 

89. SRNS1517.SR~O12.5bAag1942.RG467,NA. 

90. CINC 4 removed hia headquarters from Trnk to Maul on 1 May 1942. Lundstrom. 

91. ~S1517,SFMN012,5 May 1942;RG457, NA. 

92. SRWslS17,6 May 1942, RG457, NA eon- a trauaIakion of "5M Battle Report No. 26" For 5 May that 

reportea on the patrol of "9 type 0 fighbm." 

93. M-ur to dl CTFS 0800252, ~01072,0601452,0602462.0607542,060925~, 0612262 

94. AU of theee m-ges wer0 found in the CINCPAC Memage file, BWS, NA. 

96. M-ph by Forreat lL Biard, Captain USN Iret), Winter 1989, Vol. 10, No. 2, a epecial kw of Cryptobg, a 

publication of the Naval Crgptologic Veterans Amocktion {NCVA). Biard waa a hgubt for the- detachment 

servingAdmira1 Mer. Heredr Biard Monograph 

96. Ibid. 

98. HpotoCTFaL6d170718252May 1942,CINCPAC m~gef&,RG3S,NA. 

99. CTF 17 0723282, May 1942, CLNCPAC message file, RGS8, Nk 

105. Belconnen to COM3 0801 102 May 1942. CINCPAC message file, m38, Nk, SRNMOg88/N, 1 129 Id time 

8 May 1942; SW0897/Ii 1100 local time 8 May 1942; SRNMO90M3, Rabaul report of 8 May 1942; all RG467 

NA. 

104. CTF 17 0802522. May 1942. CINCPAC mesage Ale, RG38, MA. 

105. CTF 17 0803322 and 0803482, May 1942, CINCPAC llBaasage He, RG58, NA. 

106. SRNS1517,8Mny 1942,RG457NA. 

107. SRNS1517,8 May 1942; SRNMOBW0999,0908,0910, all 8 May 1942; SILH2n, SRNM0909 8 May 1942, aU 

RG457 MA: Wda. 

108. HC IV W X1.14; SRH 289, m7, MA. 

109. A joint CINCPAWOMSOWESPACFOR poabperation evaluation (CINCPAC 2009692, May 1942. 

CINCPAC rnasaage Ale, RGS8, MA) indkntsd that all task formas maintained akiFt radio &ace until their 

preaeme wasbverd by the enemy. The Nimitz Camd S~mutmry and the CfNCPAC messuge reflect 

poemerg measages from W form commanders to a wide audience. They were not intelligence reports. 

however. 

1 10. Biard monograph. 

11 1. Nimik to King, 29 May 1 W, King ColIdon, U.S. Narrg fiistorical Center, Operational Ardaivea. 

112. SRMHOl2n.SRNS1517,19May 1942,SRNS1617,2OMay.27fiy,and28May 1042,aIlRG#7,NA. 

113. For further information on Japanese preparations for an overland asaauh on Port Moreaby, see tbe work of 

Dr. Edward 6. Drea in MacArthr's UJfra: Cdbrsokirsg and the War Agmmt Japn, Lawrenae: University 

KansasFkesa 1991. 
Part Two: 

The Battles for Midway and the Aleutians 

The mcadbl record uf the hiprial Japanese Combid Fleet against the oombined 

Amerkn, British, and Dutch fleets following Pearl Harbor must have mitigated Japandisappointment that in the Mack on 7 December 1941 the Strilring Force failed to sink or 

damage a single U.S. carrier. It was primarily the oQective of drawing out destroying the 

U.S. that prompted Admiral Isoroh Yamamto, Commander in Chief of the 

Combined Fleet (CINC Combiaedl, to revive a earlier plan for the aptme of Midway and 

~tittotkeNavyGemdandImprial~rdStaEa.' 

In Pamamob's view, possession of this island hase, along with Wake and the Marcus 

Islands, allowed Japan to pursue its Asian policies behind an impregnable eastern shield. 

General Staff stratem disagreed with Yamamoh and his Combined Fleet st&. They 

instead to pmue a more mnsemative strategv. They reasoned that, in the long run, 

Japan could not hop to defend a chain of isolated bases far to the east of the Japanese 

~ILI&W They were ah #HIM that the United States wauld never launch an 

offensive far to the west ofanAmerhnh8se. 

In Japan in April 1942, however, it was hard to mnceiw of a military failure in the 

near future. Japanese naval superiority over the United States in the Pac=c was 

&igg&ng In carriers done it was nearly three to one (11-4 overall and 1@3, in May 

1942). In battledips, those pragons of sqwwer in 1942, the U.S. losses at Pearl Harbor 

made the dbpwiQ even more one sided (1 1-01? Until early May 1942, despite the efforts 

of U.S. sub-, Japanese naval losses7 p&icuhrly in surface forces, were Wily 

negligible, end their gains so immense that to the Combined Fleet Staff the task of 

creating an eastern shield promised to be almost effortlegs if undertaken at once. 

Thh combination of success in battle and overwhelming physical superiority greatly 

emboldened on the Combined Fleet Staff who could see the wdmeses in the 

US. Padk Fleet. They also knew that this weakness was only temporary, ~~l

h passage af the "IBo Ocean Navy* bill by the U.S. Congress in July 1940. On 7 

December 1941, the U.S. was building 15 battleships, 11 carriers, 54 cruisers, 191 

destroyers, and 73 submariner? Became of the number of ships under construction, the 

Japanese knew that the day was fast approaching when the United States would possess 

the capability to mount overpowering naval campaigns in the western Pad&. They had to 

engage the U.S. Pilcific Fleet in a climactic, viebrious showdown as early in 1942 as 

The naval staff under Rear Admiral Osami Nagaao raised objections to the plans 

implementing Admiral Yarnamoto's Midway and Aleutians strategy, Their criticism 

concerned problems of logistics in maintaining and defending such distant bases. Citing 
as counterarguments the vulnerable northeaskrn approaches to Japan, the Combined 

Reet Staff under Rear Admiral Matome Ugaki methodically ovede all objections one by 

one: Undoubtedly sharing the misgivings of their colleagues on the Naval General SM, 

but after much deliberation, the Imperial General Staff reluctantly agreed on 16 April 

1942 that this operation could occur after Fiji and Samoa had been secured." 

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Midway - Areas of Operation 

On 18 April, two short days after the Japanese had decided to attack Midway, 

Lieutenant Colonel James Doolittle, U.S. Army Air Corps, led a courageous band of 

American airmen from the de& of the carrier Ho-t in a spectacular air strike against 

several aties in the Japanese homeland. Though Japanese submarines detected its 

presence northwest of Hawaii on 10 April and Japanese radio intelligence report& its 

probable intentions on the 14th, the Americm two-carrier task force enjoyed the element 

of complete surprise. By launching land-based bomhrs instead of conventional carrier 

bombers, the Americans effectively disrupted the timing of Japanese defenses and 

eliminated in a single stroke all objections to Japan's concept of extending the first line of 

defense as far ta the east as possible and as soon as possible.' By the end of April, the 

Japanese approved a new Midway-Aleutians timetable moving this operation ahead of 

Fijamoa. The ImperiaI General Staff also chose early June for the operation to avoid 

disrupting the OceadNauru operations in mid-May! 

The centerpiece of their Midway plan was an armed feint toward Alaska followed by 

the assault on Midway. When the U.S. Pacifw Fleet responded to the assault on Midway, 

another Japanese task farce under Admiral Yamarnoto himself, lurking unseen ta the 

west of the Midway Strike Force, would fall upon and destroy the unsuspecting Americans. 

If successful, the plan would effectively eliminate the U.S. Pacific Fleet for at least a year 

&id place the easternmost Japanese base on the 180th parallel. There it would represent a 

positive threat to Hawaii and an outpost integrated with Wake and the Marcus Islands 

from which ample warning of any future threat by the U.S. would come. The occupation of 

Ad&, Kiska, and Attu was viewed as a temporary measure providing protection of the 

northern flank of the Midway forces and a temporary barrier for any immediate U.S. 

strikes against the Japanese homeland. The Alaskan operation would also provide a lift tu 

Japanese civilian morale and act as an kitant to U.S. military and political decision 

makers. When the Japanese began to implement their plans, using extensive war games 

and wmmunicrttions exercises, vital naval radio comm~cations kame virtual mirrors 

of their intentions to those who knew how to interpret them. 

JAPANESE PREPARATIONS 

The Japanese Combied Fleet's ambitious plan for the seizure of Midway and the 

Aleutians and for an epic naval battle with the U.S. PacS1c Fleet involved a massive force 

consisting of warships, transports, auxiliaries, and air strength. The two operations, 

Alaska and Midway, rquired the Combined Fleet to suppIy over 200 ships, including 8 

carriers, 1 1 battleships, 22 cruisers, 65 destroyers, 21 submarines and approximately 700 

aircraft.' For the First time since the war began, Admiral Yamamoto, who also 

commanded the First Fleet, planned to direct operations from his flagship, the battleship 

Yamato. From this vantage point he controlled the timing of the final trap, which, when 

sprung, would complete the task begun at Pear1 Harbor. He began to concentrate the 

naval elements intended for the Midway campaign in their home ports on the Japanese 

Inland Sea and elsewhere in Japan. . His preparations were interrupted momentarily by 

the Doolittle raid and the subsequent attempts 6 find the American carriers. When the 

search ended, the First Fleet prey4 to host a four-day series of war games aboard the 

super-battleship Yamato at its anchorage in the harbor of Hashirajima." 
The games bk aa their starting point a pmpctive invasion of Midway and the 

Aleutian ISM. At the conclusion of the games on 5 May 1942, Imperial General 

Headquarters issued Navy Order No.18, which directed Admiral Yamamoh to carry out 

the occupation of Midway Island ad key points in the western Aleutians in cooperation 

with the 8my.LL 

COW URFLECMONS OF JAPANESE PREPARATIONS FQR MDWA'IT AND TfI E ALEUTIANS 

The radio communications necessary to assemble, command, and control the huge 

forces being gathered b implement the Combined Fleet's plans did not escape the notice of 

U.S. Navy wpimunications analysts, who were wdly but not always able to disbetween Moresby- and Midway-related activities. Using only the outward forms of radio 

activity as they had before the war began, the U.S. 'Navy's traffic analysts slowly 

discovered and disclosed Japanese intentions in the northern PUc. When the U.S. 

Navy's cryphnalysb fully broke the MU of the Japanese Navy's General-Purpose Code 

(JN 25), they found in messages exchanged in radio wmmunications vital details of how 

the Japanese Navy intended to implement its shategy in this part of the Pdc. Together, 

U.S. Navy oommunha analysts, ss we shall see, provided key pieces of infomation 

for U.S. strategists amemhg Jqanese plans, intentions, and force levels at Midway by 

following Ja- fleet movements and war games in detail. 

Evidence of a possible Japanese intent to extend their defensive perimeter beyond the 

Wake-Marshalis-Gilberts line began to appear in naval communications in early 1942. 

The &t indication that the Japanese once again had hostiIe intentions east of the 

Marshalls occurred on 5 March, Japan the, when the Fourth Fleet under Vice Admid 

Shigeyoshi Inouye lauded a minor armed b over Oahu. Using ~pb 

hm the Marshalls refueled on the return leg by a submarine at French Frigate Shoals 

about 500 miles west of Oahy the Japanese called this project either their "K Campaign" 

or "Operation K." It was not intended as a prelude to ineon; however, thi~ feeble if 

imaginative operation actually supported an American misconception that Hawaii was 

#till a pobntkl Jam objective. 

The limited evidence deveIoped by Hypo concerning the intent behind the "K 

Campaigna was contained in three reports originated by Layton and Wrt on 2,4, and 

5 March 1942. (The atkk occurred on the night of 45 March, Hawaii time.) The &st, 

written by Laybn, said the Japanese were preparing an offensive in the Hawaiian area 

during the week of 6 to 12 March. The last, written by Rochefort, correlated submarine 

activity at French Frigab Shoals with the bombing of Oahu, concluding that the 

submarine refueled the ahraft. On 11 lldareh both Wort and Layton warned that the 

rwal threat to the U.S. Pacific Fleet in the central and northern Pdc lay in the Japanese 

buildup in ground-based aimaft in the Marshall Islands d the Mandates. All carrier 

raids - and, as it turned out, all pursuing U.S. warships - were forced to conduct their 

activities with one eye on the range of those 
During March and April, the Japanese shifted land-based air units and equipment 

destined for the occupation and defense of Midway from their homeland bases to the 

Marshalls and the Mandates. Through analysis of communications activity and 

exploitation of intercepted messages, navy communications analysts detected and reported 

daily the Japanese activities, frequently warning that the Japanese were planning an 

attack on Midway. These warnings were not universally accepted. Evaluations of 

Japanese naval capabilities by senior U.S. Navy officials in Washington were sometimes 

perilousIy inaccurate. For example, in defiance of any realistic appraisal of Japanese 

capabilities, an all-out attack on the West Coast in 1942 was expected at any time.14 

One of the Japanese undertakings cmnmunications analysts and some senior naval 

officials in Washington found most diflicult to understand was the most modest: a reprise 

of the first K Campaign. References to preparations for a second K Campaign began to 

appear in Japanese Navy communications in May 1942. Communi~tions analysts in 

Melbourne and Hawaii quickly and consistently agreed in their interpretation of the 

accumulating evidence that, from the outset, the Japa-nese intended to attempt another 

seaplane reconnaissance of Oahu. On 6 May, Hypo explained that K, or King, was an 

abbreviation for AK, the Japanese geographic designator that shd for Pearl Barb~r.'~ 

Message volume generated by preparations for this operation was much higher than 

for the earlier campaign, and there were occasional foul-ups. On 14 May, for example, 

Layton confused the K Campaign preparations with those of Midway and reported that the 

second K Campaign was a name the Japanese had assigned to their assembling Strike 

Forces.'' On 15 May, Negat mistakenly warned the War Plans staff in Washington 

(Admiral Richmond K. Turner was head of War Plans at the time) that the K Campaign 

was to be a large-scale attack on Hawaiit7 Fortunately, the second K Campaign never 

materializd. Despite the momentary breakdown in understanding on his staff, Admiral 

Nimitz agreed with his intelligence advisors in Hypo and Melbourne concerning the true 

nature of the Japanese operation and took appropriate action to frustrate Japanese plans. 

On 13 May, Admiral Nimitz ordered the commander of the Hawaiian Sea Frontier 

ICOMHAWSEAFRON) to provide surface patrols of the French Frigate Shoals area." This 

order proved to be decisive in thwarting Japanese designs for Operation K. Later that 

month, when the Japanese submarine captain prepared to take up his position for 

refueling the Japanese seaplanes, he found a U.S. naval vessel anchored in the lagoon he 

intended to use. Returning afbr two days, he found the vessel still there. Unable to fulfill 

his mission, he was ordered to withdraw, and Operation K was scrubbed," an 

unsuspecting victim of the U.S. Navy's vigilant COMINT effort. 
The vigilance of communications dysts also paid hadmme di* in their early 

re@ ofJapanese prepamtimu to attuck Midway and the Aleutian islads The rqmb 

revealed how thoroughly end completely the Japanese Navy relied on ib communications 

to fall its objectives. Warnings of Japanese intentions to expand their defensive 

perimeter eastward in the dhctim of Midway besap to appear in corn reports even 

before the JN 25 were fully readable. !he digraph AF, fbm the "A" or American 

portion of the Japanese geographic designator ~ysbm, appeared in partially readable 

mesages as early as 4 March 1942. On 13 Mar&, U.S. cryptanalysts broke JN 25, and 

Corregidor My identified AF as MidwayYm AF am again on 17 d 24 April in 

messages translated by Melbwme and Washington, Not surprisingly, 

since they probably ha red the same database, Melbourne agreed with the earlier 

iden-tion by Comgidor. The Comgidor center was evacuated to Melbourne in three 

ipcremenk 5 February, 16 March, and 6 April 1942.= OP-2@G agreed with the 

AFMidway association but as a communications designator not as a geographic 

designator, a troublesome diskhctbn when it surfaced later.% 

Indications af hostile Japanese intentions toward Alaska began to appear in 

reporb published in late April 1942. warning came from Melbourne on 27 Apd 1942, 

when the station published a translation of a message from Admiral Nobutake Kondo, 

CINC 2. In it he reqmted &arbof the ama -1 dqpes north, 14&165 degrees mt, 

an area emmpssing the region from the Gulf of Abka to Vancouver, British Columbia. 

On the same day Hypo also publW a translated Japanese Navy message concerning the 

number of planes in "AOEn and "KCN," which were identified as Dutch Harbor and 

Kodiak Island, respxti~ly.~ In the h of such compelling evidence, although the seep 

of the Japanese Sort remained temporariIy hidden, Laytan dvid Admiral Mimib and 

acials in Washington that a Japanese offensive "in the Aleutian chain seems possible in 

lab my.* 

Beginning on 1 May, Jem Navy oommunications activity fhm the vicinity of 

Japan began b increase visibly. Navy analysts soon realhi that the additional intercept 

reflected naval exercises conducted in preparation for both the Midway and Aleutian 

operations. By studying the form ad the substance of these communications, navy 

dysb &bind an abundance ddetail about dapanese plans and the magnitude ofthe 

forces to be amayed against each objective. Their reports enabled Admiral Nimite to 

counter the Japanese preparations in his own plans, particularly those for the defense of 

Midway. 

As Japanese ships began to depart their anchorages, communiations intelligence 

provided information on their future dispositions. Some movements probably coincided 

with the initial Midway Games cdbrences held on board the Yumub and the exedses 

that followed, while others were only forecasb. Although unaware of the initial 

eonferenm aboard the Yarwb, the centers at Melbourne and Hawaii reported the pairing 

of CarDivs 1 and 2 for exercise activity in home waters between 3 and 12 May and 

published the relevant hdations. In addition, Hypo provided a tramlation on 7 May 
1M, oontsining the complete agenda for an "aviation conference" on 16 May called by 

Vice Admiral Nagurrso, who by that date would be anchored in the harbor at Kago&ha. 

Vice Admiral C hmic hi N-mo 

According to the kansktio, this was s conference not on strategy but on tactics b be 

employed in an amphibious assault. It included items such as We battle for air 

supsrioriw, "the study of orgmhtions for use in dive bombing; torpedo attacks, lwmbhg 

and strafing in the battle for wiping out Id resistance"; and " . . . organization of airfleet 

aviation and fleet air unib ashore and their training." This revealing message not only 

provided a wamhg about the type of battle to expect, but it dso gave CINGPAC planners 

excellent in formulating their ph to defend Midway. As important as this 

information wahl to Admiral Nimih, it concerned only the air arm of the assault force and 

none of the surfaoe elements. Information concerning important units such as the Second 

Fleet was still needed. 

During the last days of April d into early May 1942, the status of Admiral Kondo's 

Second meet became clouded with uncertainty. Since the knd F'leet was the strongest 

surface force ia the entire Combined Fleet, it was vital that Admiral Nimitz know the 

intentions and whereabouts of Admiral Kondo at all times. Several factors contributed to 

the temporary disappearance of this important fleet its past involvement in the search for 

the Hornet and the Enterprise task forces between 18 and 25 April; its awtion with the 

"Alaskan Cha& mesage" on the 27th; its location in the Northern Area from shortIy 

after the 26&, when it was close to Soviet waters; atEd the introduction of a new callsign 

system throughout the fleet. The northern flavor of this evidence and a period of radio 

&nce observed after 27 Apd strongly implied to co~~mdcations analysts in the P8d1 

that the Second meet had returned to home waters. This conclusion may explain why the 

subject dthis fleet did not arise in the daily bulletins. Since U.S. analysts did not actually 

kuow ib whereabuts, however, internal reporb also suggested that the fleet had an 

inkrest in further offensive action "possibly in the AIe~tians.~ 
On 2 May, to clarify the reports from Australia and Hawaii, communications 

associated with the Second Fleet yielded information that w ntradicted Melbourne's 

tenhtive conclusions of the day before. A translation published by OP-20-G suggested for 

the fitst time that Admiral Kondo had inter- beyoad the northern area that involved 

the Midway Strike F~rce.~ A message originated by his Chief of Staff, Rear Admiral 

hhka Sv ' ' ' ',w wncerned the post-Midway Jaw plan to assemble portions of 

the Midway Strike and &cuption forces at Truk Shiraishi advised the 5th Base Force, 

Saipan, which probably had a detachment at Truk, that an "A" Force ad a Striking Force 

would be in Truk after 20 June. Signacantly, the message was aIso addressed to COS 1st 

Air Fleet, Rear Admiral Ryunosuke Kusaka, and COS 4. Fifth Base Force was 

subordinate to the Fourth Fleet. Span, with its excellent airfields and harbors, was an 

important b for Admiral Inouye's ~>\urth Fleet. 

UadouWy related to the 2 May message from Admiral Shiraishi was another 

message intempted two days labr. It contained an undated anchorage assignment at 

Truk for units of the Midway Strike Force and the Second Fleet. It was sent to Admiral 

Nagumo's 1st Air Fleet by an unidentified originator. Together the two messages created 

cadusion in Washhgbn and Hawaii. '90 Negat -Iysb, they suggested the existence of 

more than one dapanese Strilring Force in the central WIC. If this were true, it would be 

a matter of grave eoncwn ta the U.S. P& Fleetma W-n did not immediately 

resolve this issue b its own satWaction, but Hegat warned that their rendemus possibly 

heralded a "~secand phase to Midway, possibly involving another [sic] attempt h invade 

Hawaii." 

Here, rather uncomfortably, matters M until 8 May 1942, when Hypo correctly 

dted 1st Air Fleet elements with sevd important 2d Fleet elements, e.g., BatDiv 3 

and CruDiv 8. Hypo warned correctly of the creation of a possible Strike Force 

organization under Vice Admiral Chuichi Nagumo, CINC 1st Air Fleet. According to 

Hyp's analysis, it consisted of the four carriers of CarDivs 1 and 2, CruDiv 8, two 

battleships from BatDiv 3, and other 2d Fleet elements.%* All of these cunclusions were 

correct, and such early recognition of the Midway Striking Force gave a -or advanto tbe planners in the US. Pacific Fleet. 

Reinforcing the discovery by Hypo of a new Japanese Strike Force, on 9 May 

Melbourne inhmqkd and hamslated "1st Air Fleet Striking Force order No. 6." This 

message to the "Commander Destroyer Striking Force" ordered destroyer screens for a 

movement of many of the capital ships in the Striking Force. It codrmed beyond a doubt 

that the Japanese Navy had in Eact created a new carrier Striking Force. A subsequent 

translation on the same day reveaIed that a w*ar movement of this force was to mr on 

21 May, when ita battleships and carriers were to depart Laykin and Roehefort 

mn6dentIy advised Admiral Midb that a combined 26 Fleet, 1st Air Fleet operation 

could be expected at the end of May.98 

This advice arrived in the two major headquarters to surprisingly different receptions. 

On the 12th bth King and Nimitz recorded their views on the various scenarios reflected 

in Japanese comm~cations. Nimitz stated in his Command Summary that the Japanese 
would "attack Moresby when reinforced; occupy Ocean and Nauru starting 18 May (local); 

commence an operation May 21 with a force of about 3 BB, 2-4 CV and usual forces. The 

objective may be Oahu." Admiral King conversely published an assessment filled with 

concern for the safety of Admiral Halsey's Task Force 16, which at this time theoretically 

was within range of Admiral Inouye's air patrols. In addition to a recommendation that 

Halsey be withdrawn from the forward area at once, King also recommended that the air 

groups df both Task Forces 16 and 17 be operated from shore-based facilities east of 

Australia and in Hawaii? Both messages revealed a serious level of confusion ahut 

Japanese intentions. 

Japanese messages translated on the 13th obligingly provided clarification of 

Japanese intentions in the Hawaiian and Aleutian Islands and reduced American anxiety 

concerning a possible Japanese threat to the West Coast. The originator of this message 

was unknown, but its contents left little to the imagination of American naval officials: 

From UII: Request the ship be resuppLied with the following char&: (Send them to the 4th F'leet 

at Saipan to hold for m.) 2002,201 1,2012,2013,2015,2016,2018,2020.~ 

OP-20-G quickly supplied the identities for all charts except 2002, which was probably 

a garble: 

PO1 1-Niihau to Oahu; MlS+Oahu to Hawaii; 2013-Hawaii; 2015-Pearl Harbor; 2016-Oahu; 

2018-Seward Anchorage and Wells Bay; 2020-Weskrn Hawaii Croup, Chart Z? 

A "2nd Fleet Operations Order No. 22," intercepted and translated by both Hawaii and 

Melbourne, provided strong evidence that Admiral Kondo's Second Fleet also had interests 

in the Marianas. The translation outlined control of shore-based 11th Air Fleet units 

proceeding "to the Saipan-Guam area for the forthcoming ~arnpaign."'~ 

These translations produced an immediate change in the highly fluid views of Admiral 

Ring. On 14 May Admiral King revised his earlier and vastly different estimate of the 

situation published on 12 May and, for the second time, directed Admiral Nimitz to declare 

a state of "Fleet Opposed Invasion." (A simiIar order was published in March 1942 in 

reaction to the first "K Campaign.) Rather than again expressing his concern for the 

aircraft and ships of Task Forces 16 and 17 and calling for their effective dismantling, 

King cited four "pssibIe future enemy actions now in preparation: 1) Attack MidwayOahu line in force first week June; 2) Simultaneously attack the Aleutian Chain; 3) 

Occupy Ckean and Nauru about 17 May; 4) Reinforce New BritainNew Guinea and strike 

southeast any time be tween 25 May and 15 June. "37 

When on the 14th Layton notified Admiral Nimitz that "the forces to be under the 

command of ClNC 2 have hgun to assemble in the vicinity of Saipan," he also mistakenly 

associated the activity with the K Campaigna To Nimitz, whose view of the situation was 

not obscured by the confusion over the K carnpaiga, this report meant that even an 

impending threat to Oahu, however iII-defined and that he had posed on the 12th, was still 

at a relatively safe Admiral Nimitz did, however, implement the King directive 
and declared a state of Tleet Opposed Invasion" for the Hawaiian ad Aleutian Islands, 

iacluding Midwa~.~ 

Just as in March 1942, when WsshingtDn reacted so strongly to the &st Japanese K 

Campaign, publication of this order gave Nimib complete control of all military forces, 

including BITS, in the Hawaiian Islands. General Delos C. Emmons, Commander, U.S. 

Army Hawaii, who was not privy to Admiral Nimitz's intelligence, challenged Admiral 

Nimita's Won to defend Midway rather than Oahu. To placate General Emmons, 

Admiral Nidtz med Captain James M. Steele, USN, to reassess all the supporting 

information developed by Rochefort and Layton and to %esent the devil's argumentn at 

every opportunity ." For a time Captain Steele hme a consbnt presence with Layton, 

but Nimitz bas never prqsentd with sufficient reason to change his decision.# To the very 

end, twwever, General Emmons remained firm in his doubb despite the fact that Admiral 

Nimite to supply him with intelligence repox'ts. Oa 26 May Emmons warned Nimitz 

that he was placing too much reliance on reports of Japese intentions. Instead, he 

adviaed Nimita b base his estimates on Japanese capabilities and look for the land-based 

aircraft in the Marianas to attack Oahu,'8 After the battle General Emmone apologized for 

doubting Nimib' strategy and presented a '~eroboam" of cold champagne to him and his 

staff.u 

By 16 May both Admiral Nimih and Admiral King were in almost tohI agreemeat 

oomemhg Japme~ intentions toward Midway and the Aleutians.& The views shared by 

Nimita and King were in sharp contrast to the confusion that reigned between OP-20-G 

and the WMINCH War Plans Staff under Admiral Richmond K. Turner. According to their 

&end oorrespoadenee and a 15 May message to CINCPAC, apparently originated by 

Turner, dysb in Washingbn blkved that the strong enemy force deploying from 

Japan the last week in May 1942 was related to an offensive against northeast Australia, 

New Caiedonia, and Fiji, shrbirig between 15 and 20 June." 

The m&ion in OP-20-G and the War Plans Staff revealed by the 15 May message 

horn Admiral King's headquarters was not limited to overlooking or ignoring the 

Japanese plans for Midway. Aacording to the message for which a source within the 

generic address "COMIHCHn mot be idenmed, forces from the northern and the central 

Pacific campaigns were mistakenly mixed together. The message also incorrectly reported 

the existence of a second Strike Force by asdating a force assembling in Mpan and 

scheduled to leave on 24 May with the carrier element of the Northern Strike Force. Its 

objective, aocording to Washington, was possibly to eliminate Midway or to divert US. 

forces from the South Pacific and Alaska. The same message no@ that Howland and 

Baker might be objectives rather than Ocean and Na~ru.'~ Reacting to the possible 

presence of two Japanese Striking Forces somewhere between Japan and Truk, Admiral 

King at this pint prudently recalled dl U. S. shipping to Pearl 

On 16 May, nscthg to dapanese Fourth Fleet communications activity reported by 

the Pacific centers, Admiral Nimitz advised CTIF 16 that the Japanese had "indefinitely 

mnedw their plan to atkk Ocean and Nauru, and he ordered HaIsey to retum to 

Hawaii.& He also published his adjusted assessment of Japanese intention^,^ concluding 
that in the central and northern Pacific the Japanese would attack Midway and raid Oahu 

the first part of June. In addition, he speculated that the seaplane bombing raid of Oahu 

might be delayed until the full moon at the end of the munih (probably meaning the end of 

May). He also stated that "unless the enemy is using radio deception on a grand scale, we 

have a fairly good idea of his intention^.^" 

Aware from the behavior of the Fourth Fleet that the Japanese had not given up on 

Moresby, Admiral Nimitz provided Washington his full appreciation of current Japanese 

intentions throughout the Pacific: 

Present indicaUons [are) that them may well be threeseparate and pmsibly simulheuw erleniy 

offensives. One involving cnziaers and carriers againat the A1eutians. probably Dutch Harbor. 

Second against Port Moresby involving present forces that area. Probably reinforced third 

against Midway for which it is believed the enemies [sic] main striking force wil1 be employed. 

The message went on to indicate that his appreciation far the timing was uncertain but 

that the presence of NaLey in the south resulted in postponement of the Ocean and Nauru 

operations.52 

On 17 May Admiral King published a remarkably accurate assessment of the enemy's 

strength for the Midway and Aleutians operations: Midway attack force - four fast BE in 

BatDiv 3, CruDivs 4 and 8, CarDivs 1 and 2 plus possibly Zuikaku, at least two DesRons 

and a landing force; Unalaska attack force - CruDiv 7, CarDiv 3 (Ryrsjo and Hosho), at 

least two DesRons and troops. His estimate covered only those elements already identified 

in communications. It did not account for all the Japanese forces gathering in home 

waters, nor for all the geographic designators being used by the Japanese as apparent 

objectives. Kbg concluded his message with two critical pieces of information: the first 

and only direct allusion to the forces constituting the Japanese Main Body - ''Some 

indications that remainder of 1st Fleet may take up supporting position west of Midway" - 

and he identified Admiral Yamamoh's primary objective: to trap and destroy the U.S. 

Pacific Fleet. 53 

Precise Japanese timing continued to elude both the analysts and the mmmanders. In 

another estimate, also published on 17 May, Admiral King provided his assessment of 

when the attack(s) would occur. Based purely on inspired guesswork, he stated there were 

strong indications that between 30 May and 10 June the enemy would athck the MidwayHawaii line and would raid or even attempt to capture Unala~ka.~ 

This type of estimate was far tOO general even for planning purposes, and more 

precision was soon provided. On 18 May, within the framework of a ubiquitous 10 May 

request for weather information that may account for the seven-day delay in translation, 

Commander, CarDiv 1, AdmiraI Nagumo, revealed a fundamental detail of the Strike 

Force's attack plan. His message stated that " . .. . since we plan to make attacks roughly 

from the northwest [?I from N minus 2 days until N day request you furnish us with 

weather reports three hours prior to the time of take-off on said days . . . ."55 TWO 

additional translations of possibly the same message from different originators were also 
published the same day by Melburne and Had. They contained mother vital detail: 

Japanese planes would be Lunched fay miles northwest of AF? 

These messages did not solve the timing problem completely, but, &r weeks filled 

with ancertainty and concern bhat the right decisions were being made and executed, it is 

not dScdt to appreciate Admiral MimiWs reEbction. On the same day, he hmdiately 

sent rn- to Cl'F' 16 IHafmyl and to CW 17 (Fletcher) to mpdite their rekun to 

Pearl Harbor, and he redirected submarine search activity Opt Midway to an area my 

miles northwest of the island.s7 

On 19 May Layton drew together the recent from both Pacific centers inh a 

masterful summary that identified the main objectives of the impending Japanese 

aqmigns. He named Midway-Oahu and the AleuW, isolated theiu remlezvous as 

Saipan and Ominah, resmvely; and identified Midway and Dutch Harbor as sped5c 

Japmese objectives. The arrival of his report in Washington inadvertently coincided with 

the climax of a problem that had simmered for months between OP-20-G and Admiral 

Richmond K. Turner, chief of the Navy's Office of War Plans. The relationship, already far 

from harmonious, had deteriorated sMy she early March. At that time, newly formed 

OP-20-GI (Combat Intelligence1 and OP-20-GZ (Translation1 began to produce "mnt" 

intelligence reports based on the output of the Pdu: centem and current tmdations 

after 13 March 1942, based on the work of OP-20-GY (Cryptanalysis). The final 

breakdown stemmed from a series of minor disagreements betw-n the analysts in War 

Plans and their counterparts in OP-20-G concerning Japanese preparations for the 

Midway/Aleutians campaigns. 

The available record of the dialog between War Plans and OP-20-G reveals a very 

eve and so " 

s acrimonious relationship, touchjng on vbtudly every Japanese 

Navy initiative between 14 March and 27 May 1942.~ Digagreements were ohn so 

profound that the head of OP-204, Comdr John R. Redman, frequently had to 

rewrite the intemperate comments of the analysts who prepared responses to the question^ 

h.om Admiral Turner and his staff. The record, unfwtunately, also reveals that analysts 

in both War Phis and Newt were often unaware of the dtxiskns and actions emanating 

from both Admiral King and Admiral Nimitz, paAahrly during the critical period 

between 8 and 23 May. In addition, the record suggests that the analysts in OP-20-C; and 

War Plans were rn engrossed in their own activities that they sometimes overlooked vihl 

information concerning the Imperial Fleet redly obtainable from ttanslations from OP20-GZ and the daily reports from the Pacific centers. 

On 13 May, after the Jaw Fourth Fleet had broken off the Momsby campaign, for 

emnple, Admiral King cited several likeIy Japanese actions, including an at& on 

Midway and the Aleutians, wh he dhctd Admiral Nimitz to declare a state of Fleet 

Opposed Invasion. Two days later, after the "Hawaiian charts'' message was published, 

and after Nimitz had implemented the King order to declare an emergency, a 

memorandhm from OP-20-G was passed to War Plans. It did not mention the dialog 

between King and Nimitz nor the implications of the Japanese Navy's interest in 

navigation charts for the area around Honolulu and the Aleutians. Responding to 
questions from the War Plans staff, it focused on the much narrower views of War Plans 

regarding several ongoing and unrelated Japanese campaigns including the MO 

campaign. None of the items cited in the internal exchange contributed to or concerned in 

any way the current exchange of ideas and initiatives between Admirals King and 

Nirnit~.~~ 

On about 20 May, a face-to-face confrontation occurred between Turner and Redman, 

in which Redman learned that Turner himself was seriously dissatisfied with certain 

aspects of the Iatest COMINT repork from both the Pacific and OP-20-G. Turner specifmlly 

accused both Negat and the Pacific centers of not resolving the distinction betwccn the AF 

and K Campaigns, and for failing to perceive that CINC 5th Fleet was in fact merely a %a 

Frontier Commander who was not in command of the units that passed through his area of 

responsibility .'* 

At the end of the confrontation, Turner literally "directed" Redman to ensure that, 

unless the files showed evidence to the contrary, the COMINT centers in Washington, 

Hawaii, and Australia were all to "not comment in such a way as to indicate that Cinc 5th 

Fleet is to command any force now concentrating in Northern Empire Waters, but are to 

assume that Admiral Turner's views are c~rrect.'~' Itis significant that throughout the 

entire record of the confrontation neither party referred to Midway. Instead, through 23 

May they usually referred to an undefined and unlocated "AF" operation. Fortunately for 

the United States, Redrnan did not have the opportunity to implement Admiral Turner's 

20 May directive. 

Admiral Turner and his staff were also probably responsible for the fact that, between 

OP-20-G and the Pacific centers, a question vital to the success of U.S. plans remained 

unanswered in Washington. What was the identity of -AF,'' the acknowledged objective of 

the Japanese Strike Force? The original correlation of AFMidway had been made by 

Corregidor on 7 March 1942. It was subsequently reafErmed by Melbourne shortly after 

the center was activated on 20 March. Hawaii agreed with Melbourne on the identity of 

AF because of its position in the "A," or American digraphs in the Japanese designator 

system. Thus, among the Pac& centers there was no question that Midway was the 

objective of the Japanese Strike Force. 

Admiral Nimitz, his intelligence advisors, and Admiral King agreed with the Pacific 

center analysts. However, the analysts in OF-20-G and probably the analysts in Turner's 

War Plans staff never fully subscribed to these shared convictions. Negat believed, as 

noted earlier, that AF was acommunications not a geographic designator. Therefore, for a 

brief period between 15 and 20 or 21 May 1942, OP-20-G, and perhaps others in , 

Washington -including War Plans - were apparently overwhelmed by misgivings over the 

identity of the designator AF. Some subscribed to Samoa, others to the U.S. West Coast, 

and some to the idea that AF, as a geographic designator, was actually Hawaii itse1Es2 

Though no direct evidence exists that the following episode actually mcurred, Hypo 

was alm aware of the problem. Between 15 and 21 May, so the story goes, someone in 

Hawaii decided upon a clever method to settle the identity of AF once and for all. Some 
a&ibute the idea to the owken Wort, whose conviction was Io~

that 

Midway and AF were the same. The idea was to deceive the Japanese by fd&g a water 

shortage on Midway. With the permission of CINCP~, who had to approve all deception 

proj'ecb, a message reportedly was sent to Midway on 18 or 19 May via the cable from 

Honoldu dhcthg the station to send a do message in the clear to the 14th Naval 

Z)istrict complaining of a &&age of wate~.~ 

This order was apparently carried out promptly and with gratifying results. On 22 

May Mellsoume published the folIowting -lation: 

aTMIHIR3uoalfn~Tdcgo~-~AF~hy)airnnit~tfoIb~ngradio~gato 

hmdt 14th Dintriet: "AK" on 20th. %for Lhi;9 unit's report datsd 19th, at the presrsnt time we 

lmva only ew& hr tao week Phm mppIy ~rs immediately.' No* Haw requested 

14tb ~cb&thb-ifm&entic itatinoonhrm ideutityuAF as idw way.^ 

This message, regardless of its genesis, ultimately ended all controversy over the identity 

of AF and of the Japanese objective.@ 

The period between 20 and 27 May 1942 

was filled with heavy ~a~anese 

communications activity concerning 

~~ for the impencling operations. 

On the 20th the mter in Hawaii reported 

the appearance of tactical callsigns and 

exercise radio traffic in naval radio 

communications. These were the familiar 

signs of impe~ operational movements. 

Their appearanoe prompted Admiral Nimih 

to accelerate his own preparations. The 

reported movements of slower Japanese 

v-Is hd Omhato was clearly aimed 

at support of the Northern Force and 

prompted Nimitz to activate TF 8 under 

Admiral Robert A. Theobald. The 

movement d the Midway Oocupation Force 

Transpork &up under Rear Admid Rah Rear Admird Robert A. Thmbdd 

Tanalra was ah reported to Nimib, 

prompting him to issue the M of a series of situation estimate (on 20 22,23, and 27 

?day). To the mm cenkrs the first one was particularly noteworthy because it 

contained the following statement: "3. Our sole source of informati~n . . . is RI and CI Le., 

communktions intel6gen~e].~ 

The odm activating Admiral Thwhald was accurneed by a comprehensive survey 

of the Japanese Northern Force order of battle and a preliminary timetable. Curiously, 

Tbeobald to treat Imth this information and a shtequent refinement antaining 
more precise timing and a plan of attack as Japanese deception, and he refused to include 

it in his plans.67 

Though by no means a parallel case to Theobald's miscalculation, Melbourne rnade 

what was probably its most significant if not its only serious mistake of the entire Coral 

Seaidway campaign. Based on their analysis of communications activity and not on 

textual material, on 21 May the analysts at Melbourne incorrectly concluded that "Cinc 

Combined, while actively cooperating in directing operations in all areas, will not move to 

any particular area to assume direct command of operations.'& This statement directly 

concerned Admiral Yamamoto's *Main Bodyn consisting of battles hips, cruisers, 

destroyers, and a light carrier. This was a powerful covering force assigned to both the 

Midway and Aleutian campaigns, which, as noted by Admiral King on the 17th, was 

directly though distantly involved as support to both operations. Melbourne's ill-advised 

conclusion may in part explain why the subsequent movement of the 1st Fleet from home 

waters and its presence some 700 miles west of Midway was not detected before the battle 

was joined. Fortunately, the seeming contradiction between Negat and Hypo went 

unn~ticed.~ 

Admiral Nimitz's undiluted confidence in his communications intelligence 

organization and in his own strategic and tactical decisions was demonstrated once again 

during the building crisis in two messages he originated on 22 May; one was sent to Halsey 

and Fletcher, the other to General MacArthur. In his message to the American carriers, 

he ordered them to maintain "strict radio silence at all times," particularly among the 

aircraft "when coming in b land." The admonition was based on frequent reports from 

Hypo that he Japanese RI effort easily learned of carrier movements in and out of Pearl 

Harbor simply by monitoring air-ground radio chatter.70 The warning seems to have had 

little practical effect on the task forces. 

He also warned MacArthur that Japanese radio intelligence stations were 

intercepting air-to-ground radio contacts between Port Moresby and allied planes. He 

added that if these contacts were enciphered they were quickly and easily broken." 

MacArthur changed his codes immediately.7a This episode also indicated how closely 

Rochefort and Layton worked together. Bath messages from the theater commanders 

preceded the official notification from Corn 14 of their discovery that the Japanese were 

retransmitting Moresby-related air-ground traffic to nearby surface ships and 

submarines. 73 

It is possible the Japanese success in exploiting American radio communications in the 

southwest Pacific inspired General MacArthur to recommend a brilliant deception scheme 

using radio communications. On 24 May he proposed that Hawaii, Melbourne, and two or 

three American naval vessels in the area practice radio deception on the Japanese by 

creating the impression that a task force had remained in the New HebridedCoral Sea 

area.74 Nimitz, who by then knew that the British were not going to lend Admiral King 

the carrier he requested to support Admiral Lear~,'~ enthusiastically approved the idea.76 

The seaplane tender Tangwr (AV-8) and the heavy cruiser Salt Lake City (CA-251 were 

quickly tasked to steam around the Coral Sea exchanging carrier and intelligence tr&ic 
with each other and certain shore stations." Admire1 Nimitz prokbly never learned the 

outcome of this charade. However, the results were all that could have been anticipated. 

Japanese communications analysts detected the spurious radio transmissions and 

reprted to Admiral Yamamoto that while he and the Main Budy were en route to Midway 

anAmeriean&ta~kiorceremainedintbeCdSea~~ 

Melbourne and Washington continued to publish translations that added to the 

developing mosaic. In the radio communications of an unidentiki Base Force on 22 May, 

Melbourne discotremd a -message containing the word "Midway." The Japanese message 

requested the *aerial photographs of Midway (which were handed over to you).jm In a 

completely merent vein, the center in Washington published a message from Admiral 

Nagmw, to the "11 Air Fom" [sic] on 24 May co~~ the delivery of thirty-three 

probably ground-baaed aircraft to an mqwci&d lgcation by the Wrs of Car- 1 and 

2 d rrme unidentiikd vessel. Based on the fhct that the carriers dled at no port until 

&EX the a- on Uiway and the northern route followed to their destination virtually 

precluded a fly-off of any kind, Admiral Nimitz immediately deduced that these aircraft 

were destined to be the nucleus of a gm~pci-based air unit located somewhere on the new 

The exiskm of these aircraft and their likely purpose was subsequently 

refktd in the version of CMWAC Operatiolls Plan 29-42 promulgated on 27 May 1942~~ 

Their dxquent la was eomplebly unnoted in accounts of the carrier losses. 

hnty-five May 1942 began with Hypo's discovery of the Japanese Date Cipher. The 

Amerians now poswssed the means to determine the missing final ingredient of the 

Japanese plans: when the attack would take Application of the new information to 

translations known to contain dates relevant to the forthcoming operation allowed 

RocMatt b predict that the Japanese attack on the Aleutians would occur on 3 June and 

on Midway on 4 Despite objections from hia own staff, Admid Nhitz decided to 

base his final timetable on these dates.& 

Applying the date cipher to older traffic on the 25th, Melbourne also published a 

translation dated the 20th that alerted the Pacific Fleet to a major movement of 

eombatanta on the 22d CruDiv 8 and one battleship of BntDiv 3, the Kongo, were 

&eduled to depart the Idad Sea to rendezvous with the Kirishimu, another battleship 

in tb same division.= CruDiv 8 ad the Kirishima were destined to support the Midway 

Strike Force. The Kongo supported the Covering Group for the Midway Occupation Force. 

This deployment schedule conflicted slightly with the schedule in Fuchida. Fuchids 

recorded that the Midway Covering Group and the Strike Force left the Inland Sea after a 

fhd reheamul on the 25th. 

Ciperatiod activities in the Pacific began to accelerate very early on 26 May. TF 16 

(Hornet and Enterprise) under Admid Halsey returned to Pearl Harbor on the 26th to 

begin a whirlwid of preparations for battle." En reaction to the earlier COWINT report of 

Japanese intentions to approach from that direction, the submarine Gudgeon was ordered 

to conduct a surface patrol northwest of Midway.s7 In addition, CINCPAC Bulletin No. 72 on 

the 26th ded the electrifying news to a wide audience includimg the commander of TF8, 

Admiral TheoMd, and the other task force commanders, that the Japanese Northern 
Force had begun to depart Ominato. In the Bulletip, Layton speculated that its probable 

destination was the western Aleutian~.~ Finally, Corn 14 published the news late in the 

day that all Japanese carriers were probably at sea.@ 

(Messages concerning communications security in the U.S. Pacific Fleet were 

exchanged with Admiral King on the 26th in the course of which Admiral Nimitz again 

stated how dependent on communications intelligence his operations were. "Generally 

speaking our present intelligence is mainly the decoding of 40 percent of the messages 

copied, and only 60 percent of pssible messages are copied." At about this time Admiral 

King sent an equally candid assessment of COMINT to the Joint Chiefs of Staff. He 

attributed all of the Navy's progress in the Pacac to the success it was having in obtaining 

timely information from the Japanese naval codes. Without this information, he said, 

"disaster is pr~bable.'~ ((Ironically, within five days of Admiral Nimitz's testimonial, the 

worst fears of both headquarters became a reality when Admiral Nimib's final estimate of 

the makeup of the Japanese Midway Force fell into the hmds of a reporter for the Chicago 

Tribune, who published it in three 4or daily newspapers.) 

Twenty-seven May was a momentous day ip Hawaii, both in Headquarters CINCPAC 

and in the radio intelligence center. On the heels of TF 16, which had arrived the day 

before, the Yorktoun finally limped into Pearl Harbor still showing the damage inflicted 

during the Coral Sea engagernenLgl The god news was offset by bad news from the radio 

intelligence center: a new cipher had been introduced in the Japanese Navy GeneralPurpose Code that rendered unreadable the texts of almost all messages sent after the 

27th." 

Though the impact of the new cipher (Baker 9) was felt at once, intercept did not cease. 

Communications analysts at Hypo, with the aid of radio direction finding, were able to 

maintain their usual perspective of Combined Fleet activities including deployment of the 

Northern and Midway Strike Forces. The summary of communications activity published 

late on the 27th revealed how effective they could be even without readable messages. The 

carriers themselves, as well as the 1st Air Fleet, were silent on the 27th but received a 

message from Tokyo that was sent to a group of addressees correctly identified by Corn 14 

as the Japanese Strike Force. Seven weather ships were tentatively located northeast of 

Hawaii with the aid of radio direction Fmding. Each of the five destroyer squadrons 

associated with both Strike Forces, induding the plane guards for the Midway Strike 

Force, were identified, located, and correctly associated with the element they supported. 

A11 major commands associated with both Strike Forces were either heard or identified as 

recipients of message tratE~.~ 

Earlier messages in the Baker 8 cipher, however, were available, readable, and highly 

valuable in discerning Japanese intentions. These included a 25 May message from CINC 

5 that contained the tactical callsigns for the Northern Force, its Strike Force, and the 

Occupation Forces for "A&" and "A0";84 a vital 22 May message that stated that "heavy 

hmber force will advance to [Horomushiro] for a period of about 20 days hginning 29 

May"; a new translation of the 26 May 2d Fleet message "Occupation Force Operations 

Order Number 8," which turned out to concern a "Kazuki Detachment" or "Ekki 
Detachment.* This unit was intended to "command the 2d Combined Landing foreem and 

occupy Midway's "Eastern Island.- They also included n Combined Air Force -, 

probably also hm 26 May, hdhting the planned use of six@ "enemy engineem," ie., 

American mgimers then on Wake, in the rehddhg of Midwayym On the 28th, Howem, 

Rachef~rt announced that no radio mmmunhtions were heard from the carriers and 

escorts of the 1st Air Fleet that day and repeatsd his warning published late on the 26th 

that the carriers were at set^" (As already noted, they departed their anchorages in Japan 

beginning on the 27th in Japan and the 26th in Hawaii.) 

The reports from Hypo and Melbourne ptoduoed several reactions in CINCPAC 

headquarters. Admiral Nimitz alerted the task forces that Strike Force deploymen& were 

under way;# dispatched TF 16, now commanded by Admiral Raymond A. Spruance, fur 

Midwax ordered CTF 8 (Admiral Theobald) to maintain radio silence; wd Admiral 

Theobald that Intelligence believed that Japanese Aleutian forces included one group 

destined for Kiska and another possibly for A#u; and al& TbeoWd that dapamse 

heavy bombers would b based at Hor~musbiro.~ tonically, Admiral Theohald, who had 

only just arrived in Kodiak, again did not believe the intelligence, a11 of which was 

provided by the RI centers in ~e1bour"ne and Hawaii, fearing it was a communicationshspired ruse to draw him ~eskward.'~ He deployed his nuin force 800 miles south of his 

godialr with the objective d preventing the dapaaese Navy from getting between him 

and the eastern Akutiam and AIaskaml 

On 29 May 1942, all the centers continued to analyze Japanese fleet communications 

patterns and to tramlate earlier messips in the Baker 8 cipher. These eEorts continued 

to pay steady if uneven dividends. Negat repMted the departure of Admiral Kondo's 

Covering Group from the Inland Seam and contributed a bnslaticw concerning American 

and British diplomats being exdungdm Hyp tmnslakd messages concerning Japanese 

activities in the southwest Pacific that also were not directly related to the impending 

invasion of Midway. One interesting message in this group concerned captured 

communications perso~el from Corregidor who, during "examination," revealed detaiIs of 

oertainnavymahdhe and submariascommunications." 

Hypo also repow on current communications activity related to the forthcoming 

operations. Extremely active antisubmarine air patrols were detected in the northem 

-.IQS All task force commandem were alerted by American direction finding, which 

located three dab- submarines in northern watersm and one west of Midway. The 

Akrrgi was noted brea$ing radio dl-, although none of the carriers in the Midway 

Strike Force could be locatedm All major forces except the First Air Fleet originated 

Wc on the 29th, CINC Combined being the most active;lW five Northern Force DDs 

were noted continuing their movement from Sasebo to Ominah to Abukuma that had 

begun ear lie^.^ Ah on the 29th, COS 2 was noted sending s me- to all forms under 

his command with information to the Skrike Force and khe Mdhem Fwee signifying that 

he was sup- both operations. 
Japanese Submarine Akagi 

Despite the evidence from COMINT that the Japanese Northern Force was now 

approaching its objective, Admiral Theobald had not originated a plan of operations by the 

29th.'" In the absence of a plan from Theobald, biit in receipt of Admiral Nimitz' message 

of the 28th outlining the probable Japanese plan of the commander of the 

Northwestern Sea F'rontier asked CINCPAC if he should "evacuate white personnel from 

Attu and ~iska."''~ CINCPAC responded mrmakively,115 and CTF 8 (Theobald) waa given 

the responsibility for conducting the evac~ation."~ Understandably alarmed at the 

COhisEC implications of a successful Japanese attaek on a base with communications 

facilities, the "Vice Chief of Naval Operations" (probably the Director of Naval 

Communications) sent a message to all bases in Alaska to '%urn all U.S. Naval and 

combined cryptographic aids except those currently effective . . . .""5 Unknown to anyone 

in Washington, the overall situation concerning American communications security was 

even worse than suspected. 

Far from enjoying tohl anonymity, American preparations to defend Midway were on 

the verge of discovery. Japanese trac analysts reported that 72 of 180 messages from 

Pearl Harbor were "Urgent." To them this extraordinary increase in high-precedence 

messages in Hawaiian and Alaskan waters suggested that a U.S. task force was at sea.' 

Their suspicions were supported by a Wake report that U.S. patrol planes were operating 

far from Midway.'l7 In addition, a COMiNT detachment traveling with Admiral Yamamoto 

reported that a U.S. submarine just ahead of the Transport Group that had left Saipan on 

the 28th had sent a long urgent message to Midway on the 30th suggesting that the 

transports had been discovered."' hcredibly, all of the discoveries concerning U.S. 

activities made by Japanese CQMINT in Tokyo or in the Yamato were withheld from the 

Midway Sbike Force by Admiral Yamamoto. They were not reported to these key 

subordinates either because he assumed they had heard the Tokyo broadcasts or because 

he refused to break the radio silence he ordered when they departed home waters.'lg 

On 30 May 1942, the Yoratown (TF 17) slipped out of Pearl Harbor probably detected 

by the COM~ detachment on the Yamato, but, in an equally bizarre leap of logic, this fact 
too went unreported to the rest of the Strike Force huse of radio silence restrictions."' 

Although the lmation of the Japanese Mke Force was unknown, mt that it was "at 

sea: the U.S. Padic Fleet carrier task forces sped on khir sqamb ways to positions mar 

Midway that were dictated by Momation provided by COMRW.~ 

Each center continued to march feverishly for earlier readable messages that would 

conkibute to CINCPAC'S decision-making capab'ity, but, as tk supply of rn- grew 

dler, their efforts met with 1- and less success. The aih in Melbourne found an 

imporh~t message dated the 27th that contained the future deployment schedule for a 

unit of heavy bmbers. Ten Type 1 heavy bombers from bilisawa Air based at Kiwazu 

were scheduled to depart for Wake in a thee-stage move begimhg on 1 June and ending 

on the 3d. This deployment would place them within range of Midway in plenty of time to 

participate in any naval action beginning on the ?them Moreover, should the Japanese 

succeed in mizing Midway, the= bombers represented a potential threat to Hawaii. 

Plimita reacted to this information by issuing a Wwxtbn to his OP P1an.lzs Negat, 

through andpis of communications activie, codhd once again that the carrier Ayyo 

was at sea with the Northern Forces and reported that the commander 6 AAF was 

probably aboard the Ah, thus explaitYing the thirty-three land-based ahaft hard the 

miem in the Strike Force. lBQ 

Ssarehing through mewages sent prior to introduction of the new cipher, the dpts 

at Hypo ah made the im-t discovery on 8 May 1942 that fighter pnots from CarDiv 

5 awrk Zuikuku were @erred to a probable Northern Force unit leaving Orninato on 

the 26th.lN This bvery completely ruled out the possibility that the Z&u could be 

called upon to wrpport either the Aleutian or the Midway operatiom o bey also found a 

messuge oftbe ZZd pdd1y from Admid Nagumo, CINC 1st Air Fleet, addressed to all 

four h in Caram 1 and 2, Cdiv 8 and a battleship in BatDiv 3. All were dled to 

a conference aboard the Akgi on the Mth, which meant that a1 were dl in port at that 

time - an important insight into the Strike Fom's dedule.'" With the aid of ditection 

finding;Hypo again hted the weather ships detected earlier. New data now placed them 

on the 155E line stretching hm Kamchatka to below 25N.la7 

Admiral NimiWs operation plan estimated that the attack on the Aleutians would 

probably come on 3 June. With this in mindI a miniclimax began at Fort Rkhdson, mar 

hhomge, part of the Alaska Defense Command, when at 19202 on 2 dune the 

commander reporhi Japanese carrier-based planes less than 400 miles mth of KU." 

The Commander, Alaskan Section, to whom this report was addressed, incorrectly 

assumed the infomation came from an "RDF fiXmHrn This report supplemenbd Bdleh 

Number 79, already sent to the bsk forces, which contained taw news that a navy patrol 

plane had made contact with Japanese aimraft 500 miles from Midway at 21402 on 1 

June,'pg 

Another highlight of the events of 2 June was the appearance of "unusual enemy radio 

activiw on a large den west and north of the Dutch Harbor radio direction finding Pik 

Dutch Rdr also reported bearings of 320 and 034 degrees. These bearings were 

probably related to weather-reporting Mam, which the sution could not ordinarily 
hear.- The same weather-repwting ship exbdhg from Kamchafka bo 24N on the 155E 

line were again recoded by Com 14 in their summary for 2 June 1942." 

Corn 14 and the center in Melburne both enlarged on the earlier evidence that 

Japanese bombers from up to possibly ahree Air Attack Forces were being relocated to 

positions in the Marshalls and to Wake,'= where they posed a threat to Midway's 

defendem. As noted earlier, these aircraft potentially represehted a large grouud-bzmd 

bomber unit on Midway that would be a gerious threat to Hawaii if ths Jam seized 

Midway. Melbourne's analysis of air activity in the Bhmhalls ppwided an important 

insight into the whereabuta of the Japanese Occupation Forces. They ooncluded that 

heavier than mml air reconnakance, coupled with unusually heavy message traffic to 

a destroyer unit in the same area, meant that fhe &cupation Force was approaching the 

Mamhall~.~ 

Older tmfiic again paid dividends when three mssages sent in the previous cipher, 

Wet 8, wem intercepted between 31 May and 2 June. The brief but readable contents of 

two of the messages were inconsequential, but the third, intercepted on 2 June, concerned 

casualties on an unidentified carrier. One of the de pupa represented a lost carrier, the 

name of which ended with Mu. Melbourne am&sb masoned that, shm the two adem 

of CarDiv 5, Sbb d Zddu were still atloat, the lost vessel must be Ryuddu. 

Clearly, Ameh cryptanalysts were having trouble with cerkin oode group memkgs 

within the General-Purpoas Code. They had not yet veritied the identity of the Japanese 

carrier (Slhohol sunk on the first day of the Battle of the Coral Sea dmoot a month 

before." 

Negat did not publish any product related to the forthcoming operations on 2 Juae 

1942. Citing OM estimates, however, Admiral King's headq- hd a summary of 

"esthmhd ch8nges Orange Ple&tn that oonbiImd serious errom. Most -t we= 

two~pe~totheJa~MainBodyunder~alY~todhthe 

Strike Force under'Admiral Nagumo. ON1 incorr&ly estimated that BatDivs 2 and 1, 

CarDiv 4, and DmRon 3, parts of the Main Body, were still in the *Bonins-home waters 

w" In fact, on the following day this force was approaching the weetern edge of the 

c~xluded hnt west and northwest of Midway.- Perhaps more imporbfly, OMI chose 

this moment to report the pmme of a fifth carrier, and identi6ed that carrier as the 

Zuiku&u." Fortumhly, Admiral Nimih and his intelligence staff had 00- in the 

information being generated by the centers in the Pacilk, and this ON estimate waa not 

acted upon or repeated to the task forces oflbiidway. 
THE BATTLES BEGIN 

As predicted by Hypo, the Japanese offensive against the Aleutians began on 3 June: 

Japanese carrier aircraft attacked Dutch Harbor at 1555210655 Io~ally.'~~ A little over two 

hours after Admiral Nimitz repeated his second alert, while the Japanese renewed their 

attack on Dutch Harbor, Midway notified him that the Japanese 'Wain Body" was sighted 

at 21002 by a patrol: plane on a bearing of 261 degrees and a distance of 700 miles from 

Midway.'= Eighteen minutes later, apparently as a result of Hawaii's receipt of the report 

of analher patroI plane, CINCPAC learned that a second group of ships had been sighted. 

The second, a smaller group of warships and cargo vessels, was located 470 miles from 

Midway. Nimitz immediately fomarded this information to the task force commanders, to 

Admiral King, and to General Emmons, COMCENHAWDEPT.'~~ TWO hastily prepared 

elarZmtions were sent later that stated his belief that the forces sighted were the "attack 

and occupation force," the most distant consisting of " 11 ships course 090 speed 19." The 

Strike Force was "expected to be ~eparated.""~ AU of this information and the roles of 

CINC 5, CINC 1st Air Fleet, and CINC 2 were included in CINCPAC'S Bulletin Numkr 81 

sent in the late &moon of 3 June.*' 

Corn 14's daily report was released in mid-afternoon on 3 June several hours before the 

Alaska operations began. Zt was a timely summary of the knowledge gained from 

translations and other analysis. Most of it quickly found its way to the task forces. Hypo 

Mated those units "interested in operations against U. S. possessions." Their report 

correctly if too briefly identifled Admiral Yamaxnoto, CINC Combined, as "in general 

charge." The actual role of the First Fleet as "Main Bodyn ofthe two operations continued 

to elude analysis. Hypo reported that Admiral Yarnamto, the mrnmder of this fleet, 

"appeared only marginally interested in the current operations. All the other -.or 

commanders were correctly identified: Admiral Kondo, CINC 2, whose battleships, 

cruisers, and destroyers supported both the Strike and Occupation Forces, was 

characterized as "in command of invasion forces in Midway area"; CINC First Air Fleet as 

"in command of Striking ~oiees against Central PacEi~ bases; and CINC Fifth Fleet as "in 

command of invasion and Striking Forces in N~rth."'~' 

Cam 14s analysis was hampered by the fact that no traffx was originated by any of 

the Japanese commanders &r either 28 or 29 May 1942. Sice the entire Combined Fleet 

observed radio silence and a new cipher was introduced in JN 25 at the same time, 

analysts were left with virtually nothing to analyze except communications contacts 

initiated by shore-based radio stations, and old messages to and from ships at sea in the 

Baker 8 cipher. In the Iatter category was an errant transmission from the cruiser Nagaru 

revealing her role as flagship of the Strike Force's plane guard deshyers, a fact that was 

immediately conveyed to the CTFs.'" Shore-station camrnunications, however, remained 

active. Though messages originated by shore stations could not be read, their contacts 

revealed that Wake was not a ~topping-off place for either the Strike Farce or the Invasion 

Force. 
Among the many topics demanding Admiral Nimitz's attention at this time was the 

need to ensure an adequate flow of information into his headquarters during the 

forthcoming battles. Recalling the paucity of information available during the Battle of 

the Coral Sea and mindful that certain matters concerning enemy losses in that battle 

were still not resolved, Admiral Nimitz sent a quick reminder to Midway and to CTFs 4,7, 

9, 16, and 17: "Successful and timely employment Striking Forces . . . almost wholly 

dependent on reliable combat intelligence with emphasis on enemy composition, psition 

and condition. Damage to enemy must be carefully evaluated and reasonably certain 

results be reported. rCeprts muslt get through promptly."'44 Unfortunately, the record of 4 

June suggests that hia guidance could not be followed by thost: he most depended upon, the 

carriers and the 3178. Obviously full of confidence in his intelligence and his plans for the 

next day's action, however, Admiral NMi& also sent this encouraging message to Midway 

and dl task force commanders at the eleventh h~ur on 3 June; "The situation is 

developing as expected. Carriem our most important objective should soon be ImWd. 

Tomorrow may be the day you can give them the ~orks.*~'~ 

(The next day, 6 June 1942, in apparent response to the Nimih message cited above, 

Washington directed the use of new terminology k describ mmmunications intelligence 

and new cryptographic systems for its transmittal. The abbreviations "DI" for decryption 

intelligence, 'TI" for tr*c intelligence, and "RIn for radio intelligence were now 

mandated. Any message or report containing DI was to be transmitted in the COPEK 

system. Information from 'I% alone was to lx sent in the CETYH system. Both systems were 

apparently available to all GOME addressees since there was no immediate change in 

distribution.lw It is impossible to determine if this guidance was a help or a hindrance. It 

is certain, however, that, during the battle, it was ignored by everyone.) 

Just after midnight on the morning of 4 June, Nimitz realized that he had not yet 

advised the task forces how far the "Main Body" was from Midway. Accordingly, he 

repeated messages sent earlier concerning its course and speed and included the 

information that this force was now "574 miles" from Midway."' All remained quiet until 

shortly after dawn when at 1804210604 local time on Midway on 4 June, a reconnaissance 

plane from Midway spotted two Japanese carriers and their escorts and transmitted an 

electrifying report that was immediately re-td by Admiral Nimitz to his task forces, to 

Admiral King, and to General Emmons: "Many planes heading Midway from 320 distant 

150 miles!*lM Less than half an hour later, at 18352, Midway was struck by Japanese 

carrier aircraft.'" History does not provide an explanation of why the Japanese chose to 

launch aircraft 150 rather than 50 miles from their objective. It is possible that the 

original translation was somehow flawed. The flaw could have been in any of several 

places, for example, the preparation, transmittal, or intercept of the text of the message, or 

in an incorrect code group meaning. All of this mattered very little on 4 June, however, 

when the Japanese carrier aircraft were spotted on their way to strike Midway. 

Of the more than 200 units of the Japanese Combined Fleet deployed in the Alaska 

and Midway operakions, no fewer than 129 were either warships (1 13) or submarines (1 61. 

At Midway, however, primarily because of the requirements of their complex plan and 
their 1- in the Coral Sea, the Japenee could actually produce but 4 -IS, 17 escorts, 

229 aimaft, and 17 seaplanes. The remaining Japanese vessels and aircraft were either 

committed to the Northern operation or were too far away to support the carriers.'" 

Compared to the oruvshing Japanese Strike and -tion Fom, the United States 

Navy was able to musk only seventy-thme ships (forty-seven -hip d twenty& 

submarhes1. However, the United Staks was able to eo~lcentrak its forces ad produce at 

Midway a slight advantage where it counted the most, at the scene of the battle. The 

Unikd States had 3 carriers and 22 escorts at sea, 234 aircraft afloat, and 110 at Midway. 

All of these vessels and aircraft, as well as a few of khe submarines, were on the scene at 

Midway on the morning of4 Jane f 942. 

h addition, Admiral Nimitz and hia task force commanders had other less tangible but 

invaluable advantages as well: advance knowledge of the identity of Japanese objectives; 

virtually the entire Japanese Midway and Aleut& Strike Forces order of battle; the 

orgmization of the Midway fomes, is., !Mking Force, &cup&ion Force, Invasion Force, 

&.; the plhinmry and htlal timetables of the Midway and Aleutian Striking Forces; the 

general dirdtl from which each force would approach Midway; and the Midway 

Striking Force's plan of at@. All of ahis information was supplied by communications 

intelligence in time b influence decisively the provisions of Add Nimite's Operations 

Plan 29-42. 

As foretold by Mrt and Laybn, the Battle of Midway ommed three days before 

Admiral Yamamoto pl& b assault the island with his landing forces. The Marines 

and ~ilors in their prepared positions on Midway, the Navy and Marine Corps flyers on 

Midway, the submarines in Task Force 4, the patrol aircraft in Task Fume 7, the surface 

patrols in Task Force 9, the B17a in the 7th Bombing Cod, and the carriers of Task 

Forces 16 and 17 dl were ready for the fighL They were dy Wuse Admiral Nimitz 

was abIe to position them in the relative certainty that the attacking Japanese warship 

and carriers would be where WMINT had predicted, at the day and time COMINT had 

provided. 

In the ubsence of Japmese radio communications from the ship approaching Midway 

on 4 dune, Hypo reprted to Admiral Nimitz how they had diqmd of their intercept 

resources to deal with the crisis. Watches were doubled under a "Condition 1" at the 

intercept station on Oahu,151 and a combination radio direction finding and intercept 

fadiw was temporarily estabiiished on Midway. Intercepted -c had accordingly 

but not from the onrushing Japanese task fom. Hypo concluded that "excellent radio 

silence Q king mainaed despite the reported attacks on them." Thanlts to the 

additional Man finding dispositions on Midway, as weH as the reports received from 

naval akrafk of all types and from the army bombers operating from Hawaii and Midway, 

Admiral Nimitz w nevertheless in an excellent psition not only to keep kack of events 

but actually to mnhl the movements of his own forces in relation to the atJ-. Tbis situation was in sharp eontrast to the Battle of Coral Sea only a few weeks 

before, when CMCPAC was virtuany blind to unfolding events. 
When radio silence was finally broken by the attacking Japanese at about 1200 

Midway local time, their frequencies were immediately intempted and bearings reported 

probably by the temporary station at ~idwa~.~~~ Except for encoded submarine 

communications, radio traffic consisted largely of plain language air-to-ground exchanges 

between carrier aircraft and the carriers that ended when the carriers themselves were 

lost. This information became part of an immense body of data concerning American 

efforts to learn the locations of the several Japanese task forces involved in the battle. 

Admiral Nimitz's appreciation for the magnitude of his victory came gradually from 

visual observations and not from COMINT. Visual observations, however, were rife with 

ambiguous directional and ship identification information. More than once cmr;PAG 

pleaded for more precision, particularly in those reports concerning the Japanese 

car13ers.l~~ In the absence of Japanese carrier communications, it was finally from visual 

reports that he learned in mid-afternoon of the 4th that Admiral Nagumo had probably 

lost the four carriers of his Strike Force.lsq Precise ward of Nagumo's loss did come from 

COm, however, but not until 6 June when Hypo reported that Admiral Nagumo 

"appeared aboard the heavy cruiser Nagcwu sometime this morning, apparently having 

lost his flagshipTm and Melbourne reported that the Chief of Staff, 1st Air Fleet, was also 

addressed aboard Nugara. 

As dawn approached on the morning of 5 June, Midway itself was safe. At midnight 

the night before, Admixal Nimitz had sent his heartfelt congratulations in a message to 

the task force commanders: 

You who participated in the Battle of Midway May have writtena gloriow page in our history. I 

am proud ta be associated with you. I estimate that another day of a11 out effort on your part will 

compleb the defeat of the enemy. 

That morning there was a growing but not universal consensus that the Japanese 

were hurriedly leaving the area. At one point during the morning of the 5th, CINCPAC 

originated a message to both TF 16 and 17, to Midway by cable, and to COMINCH, that the 

Japanese "will attempt assault and occupation Midway regardless past 10sses."'~' In 

either case, the task of fmding the enemy and inflicting still further punishment was 

preeminent. No one in CINCPAC headquarters was aware that Admiral Yamamoto had 

postponed part of the Northern Force's operations and temporarily diverted both the 

Second Strike Force and the Covering Group to assist Admiral Nagumo in his extremity. 

They were aware, however, of a report from Melbourne on the 5th that stated that CarDiv 

3 "shows slight indication that unit may proceed southward to join forces in Midway area." 

Fortunately for the American cause, Admiral Yamamoto vacillated for several hours 

before deciding to cancel his orders and restore the forces diverted from the northern 

area.'% 

In sharp contrast to the voluminous reports from Hypo and his intelligence staff, a 

more truncated view of events was recorded by the CINCPAC War Plans division. Their 

daily report to CINCPAC sheds an interesting light on the treatment of information 

obtained from intelligence sources. While adding nothing positive to the general body of 

knowledge, their efforts are of interest because they were recorded in the CINCPAC War 
Diary; they again demonstrate how, as in Washington, a war plans staff pup in a major 

headquarters experienced acuity in communicating with its leadership. In the CINCPAC 

War Diary for 5 June, War Plans summarized the Japanese Order of Battle of the Strike 

and Occupation Forces only and the results of the battIe of 4 June on both sides. Their 

report did not reoord losses of a fourth Japanese carrier or the Yorktown, though by 

0503352 1041635 Hawaiian War Tie) CmCPAC knew of both the Japanese losses and the 

condition of the Yorktown. The' summary ended by documenting the third air attack on 

Dutch Harbor and the sighting reports of two CVs southwest of that port, information 

probably received from Admiral Theobald's reprewntati~e.'~ 

On 6 June, Hypo was aware of and quickly reported the implications of the fact that 

the flag of the 1st'Air Fleet, which was a recognizable communications entity, had moved 

from the Akagi to the cruiser Nagara. Analysts at Hypo also reported on the 6th that "at 

1710 on 5 June ClNC Combined began sending tactical -c thus breaking his silence 

that began 28 May." Other significant items in COMINT reports for 6 June included the fact 

that 4AAF was prepared to provide air cover to all retiring elements; a call for CacDiv 5 

prohably to send the ZuiMu to the area; reflections of a U.S. air attack on Japanese 

cruisers, possibly the Mogami and the Mikurno; .,! the Eact that no carriers had been heard in 

the Midway area for twenty-four hours; and the startling revelation from radio direction 

finding that Admiral Yamamoh himself was in the North Pacific possibly in company 

with two divisions of battleships. This report represented Hypo's discovery of the Japanese 

Main Body.lBO 

In a War Diary entry for the 6th, War Plans summarized the actions of the 4th and 

5th. The Japanese were dewribed as "retiring" as the U.S. search continued. The 

assessment of Japanese losses did not reflect the by then well-known fact that all four 

carriers were lost: two CV lost; two CV damaged; two BB damaged; two CA damaged; two 

AP damaged; and all aircraft either lost or badly damaged. Concerning the Yorktown, 

which on the 6th was struck by two hrpedoes fired by the Japanese submarine I168,"' the 

War Plans entry noted only that attempts at salvage (from bomb damaged inflicted on the 

4th) continued. Finally, the entry also noted that Dutch Harbor experienced its fourth air 

attack.'@ 

Admiral Spruance decided that the Battle of Midway ended on 8 June 19$2.183 GOMINT 

for 7 and 8 June chronicled the fact that the J8panese were withdrawing in two echelons. 

One group moved southwest toward Saipan under the protection of the 4AAF and the 

other, which included Admiral Yamamoto, was withdrawing to the northwest with air 

support from CarDiv 3.1M All activity was conducted under the direction of Admiral 

Yamamoto, who was now personally directing the final phases of his Midway operation. 

Routing of a message for CINC 1st Air Fleet from Ominato ria the carrier Ryujo suggested 

to Hypo that possibly the admiral aboard this carrier from CarDiv 3, Rear Admiral Kakuji 

Kakuta, was the new senior officer in the 1st Air Fleet. Subsequent communications 

activity was to negate this suggestion by indicating that Admiral Nagumo was in fact still 

aboard the Nagamfg5 Still sensitive to the fact that a missing Japanese carrier was a 

potential problem, Layton again sounded the alarm that the carrier Zuikaku could not be 
located. His report suggested that it may have been joining the forces withdrawing from 

Midway. Layton also reported that COM~NT indicated no CVs remained among forces that 

attacked Midway. lBs 

The disparity between current events and War Plans reporting continued for another 

day. An entry in CINCPAC*~ War Diary by War Plans on the 7th suggested either that the 

entry was written before the CO~T report became available or that War Plans analysts 

were unwilling to accept information from that source. Instead of reporting that all four 

Japanese carriers had been sunk by American flyers, the entry recorded "incomplete 

reports" from army bombers and from TF 16 that a possible fourth Japanese CV had been 

sunk. In the Aleutians, it reported contact with the Japnrtese was being maintained by 

PBYs but "no effective attacks by bombers or torpedoes." There was no reflection of the 

status of the Yorktown, which sank at 05012 on 7 June 1042.'" 

By 8 June COMI~ from both Melbourne and Hawaii was able ta report that the 

withdrawing Japanese occupation forces under Admiral Kondo appeared to be headed for 

Saipan. Radio direction fmding placed CINC Combined almost due west from Midway, 

and the remnants of the Strike Force appeared to be heading toward Japan.'@ Layton's 

report for the day once again warned that the Zuikaku appeared to be active and might be 

en route to join the withdrawing forces.lW Hypo codided to its War Diary that the 

Japanese in Tokyo had "commenced radio deception and were attempting to give the 

impression &at a large fleet is maneuvering." In its daily report for the Sth, Hypo noted 

that tacticaI calls for up to twelve tactical units were traced to Tokyo through the "sloppy 

communications practices" of the Tokyo operator and DF.170 The 8th was the final day that 

the CIMCPAC War Diary contained any information from War Plans concerning either 

Midway or the Aleutians. It recorded that the enemy continued to withdraw from Midway 

and that bad weather in the Aleutians hindered operations. Though the war continued in 

the Aleutians for several months, the Battle of Midway thus had three endings: on the 6th 

when Admiral Spruance turned away from his pursuit of the retreating Japanese; on the 

7th when Admiral Fletcher's flagship, the Yorktown, finally sank beneath the waves; and 

for CINCPAC, on the 8th; when his diary no longer reflected an interest in the defeated 

Japanese forces. 

CONCLUSIONS 

After the battles of Coral Sea, Midway, and the Aleutians, the invaluable 

contributions made by communications intelligence were recognized by senior naval 

officials in Washington and Honolulu. In their words, communications intelligence had 

given the United States a advantage" over the Japanese.17' In few battles before 

or since would the navy possess an enemy's order of battle, their plan of attack, and their 

timetable, a11 of which had been provided to the naval high command by the 

communications intelligence units in Hawaii and Australia under the direction of 

Commander Joseph J. &hefort and Lieutenant Rudolph Fabian, respectively. 
With their performance during this period, both centers reclaimed the synergism that 

had marked their efforts before Pearl Harbor. There is no doubt that, had he lived to 

receive the Jhtinguished Service Medal - that was eventually posthumous~y awarded by 

the secretary of the navy in 1986 for his efforts to support CINCPAC prior to Midway - 

Commander Rochefort would have said that the medal truly belonged to the entire 

communications intelligence effort in the (Fabian too was recommended for a 

DSM by MacArthur. Like Rochefort's, it too was not approved.) 

On the eve of each of the battles fought in May and June 1942, Japanese 

communi~tions security attempted to prevent U.S. monitors from penetrating the navy's 

intentions. It was not until the end of May, however, that radio silence effectively 

eliminated access by Hypo, Melbourne, and Washington to even those few messages 

related ta the impending operations that were exchanged outside the confines of a new 

cipher and a new callsign system. Fortunately, the Japanese efforks to protect their secrets 

came too late to prevent what the world now knows was a major U.S. intelligence 

achievement. 

Armed with the support of excellent communications intelligence and of his superiors 

in Washington, CINCPAC was able to sakisfy all three af Clausewitz's "principles of 

warfare": decision, concentration, and offensive action. Prior to the invasion of Port 

Moresby, his fast carrier task forces successfully turned aside the Japanese strike force, 

virtually eliminated the effectiveness of Carrier Division Five originally scheduled to 

participate in the Midway operation, and forced postponement of the Japanese strikes on 

Ocean and Nauru by the judicious placement of CTF 16 when it was certain that the 

carriers Hornet and Enterprise would be spotted by Japanese patrols. 

The same support from communications intelligence also allowed CINCPAC to deploy 

submarines, ships, BITS, B26s, fighters and observation planes to defend Midway and the 

Aleutians. By knowing the approximate dates for the planned attacks on the Aleutians 

and Midway, CINCPAC successfully disengaged his carrier task farces from the South 

Pa&c after Coral Sea without being observed; he successfully redeployed them precisely 

where they could surprise the unsuspecting Japanese Strike Forces. 

Without doubt these were major contributions to a truly decisive American victory, a 

victory of the magnitude of Salamis in 480 B.C. and Jutland in 1915. As a result of the 

Battle of Midway, the U.S. Pacfic Fleet permanently frustrated all Japanese ambitions to 

establish a defensive perimeter anchored east of the Marshalls. Most importantly, 

however, the victory exposed to U.S. Navy planners Japan's incapability to wage effective 

carrier warfare in the central Pacific. Amidst its unrivaled success, however, this story of 

the contribution of communications intelligence is not quite complete. 

Of the mobile detachments on the Lexington, the Yorktown, and the Enterprise, which 

accompanied the U.S. task forces (the Hornet had no detachment at Midway), we know in 

dehil from the postaction recollections of Captain Forrest Biard, USN (ret) - who served 

under Admiral Fletcher, CTF 17, on the Yorktown - the type of contribution probably 

made to the commanders' tactical decision-making process during Coral Sea. At Midway, 
however, we know only that they "provided valuable information after conbct was made, 

through intemption of Japanese plain language ~eports.'''~~ Thus until survivors reveal 

the detailed contributions made by communications inblligence to the tactical decisions of 

Admirals ETetcher and Spnance, CTF 17 and 16, respectively, the cavlm chrunicIe will 

be missing that prt of the story. (Admiral Fullenwider, who supported Admiral Fletcher, 

is dead. Admiral Spruance was supported by a COMINT detachment for which the linguist 

was Captain Gilven Slonim, USN (ret). On 16 May 1989, Slonim advised the author that 

he was preparing a book about his experiences in the "RI" detachments that he plans to 

have published "in time for the 50th anniversary of the Battle of Midway.") 

EPILOGUE 

The Battle of Midway continued long after the combatants retired. Because of the 

confusion that surrounded the nascent and relatively unfamiliar U.S. Navy policies 

governing secrecy and need to know in 1942, the Battle of Midway was refought in the 

newspapers and courthouses of three major U.S. cities - New York, Chicago, and 

Washington - for several weeks after the battle actually ended. At issue was how the 

Navy knew of Japanese plans, how that knowledge came into the possession of a 

newspaper reporter, and how the government should handle a serious security violation. 

In the end no one was ever formally punished for revealing to the public the role 

communications intelligence played in the Japanese defeat. Whether the Japanese ever 

discovered that U.S. cryptologists had successfully penetrated their most secret 

operational ccde, or even suspected the magnitude of the warning provided by COMINT, 

remains a matter of conjecture to this day. At the time, however, off~cials within OP-20-G 

were certain that subsequent almost draconian corrections in Japanese oommunications 

procedures and cryptography were traceable directly to the following events. 

On 17 May 1942, the survivors of the Lexington were en route to San Diego and San 

Francisco ahard the USS Barnett and the USS Elliot. (One account said that Admiral 

Fitch and Captain Sherman were aboard the transport Chester.) Anticipating their arrival 

in the United States, crNcpAc sent the following message to Admiral Fletcher, CTF 17, 

with information copies to COMINCH and the Commandants of the 1 lth and 12th Naval 

Districts: 

It is imperative that all survivors Coral Sea action being returned Mainland be instructed that 

they are to refnin from any mention of the action upon tbeir arrival west coast port. Corn11 ia 

. requested berth tramports where debarkation can be conducted without contact with newsmen. 

AU pemmd will probably require reoutfitting. There will be no publicity regarding this matter 

until Navy Department release. Barmu and Elliot will stop at San Diego to dixharge srcesa 

personnel en route San ~rancisco.~'~ 

Despite these precautions by cINCPAC, events aboard the Barnett resulted in even more 

-damaging revelations than those CINCPAC had hoped to prevent. (In ancillary actions, 

CJNCPAC learned that medical reports filed in Navy Bureau of Medicine channels revealed 

the status of American- carriers after the battle. In a hasty message on 3 June 1942, 
CINCPAC notified COMINCH and requested immediate action to suppress the errant 

reports.17' At 2050 on 8 June 1942, COMINCH sent the following message to CINCPAC: 

Contentsof your 311221 May were published ahmet verbatim in sever& newspapers yesterday. 

Article originated with correspondent Stanley Jobaaon Isicl embarked on [USS] Barnetr until 

June 2d. While your deapatch was addressed Task Force Commanders it was sent in channel 

available to nearly all hips which emphasizes need of care in using channels para. Corninch 

investigating on Bar- and at San ~ie~o."~ 

CINCPAC'S message of 31 1221 May contained hi final appreciation of the Japanese order of 

battle prior to Midway. 

True to his word, COMINCH immediately convened several formal inquiry panels, 

which began gathering depositions from witnesses. The panels inquired into the 

circumstances aboard the Barnett, which, in addition to most of the crew, carried the 

executive offlcer of the Lexington, Commander Morton T. Seligman, and a newspaper 

correspondent, Mr. Stanley Johnston, back to the United States, and in Chicago in the 

headquarters Colonel R.R. McCormiek's newspaper, the Chicago Tribune, where the story 

had ~riginated.'~~ According fa Admiral King's biographer, Thomas B. BueIt in Mmter of 

Seapower, Admiral King "was in a white fury at his headquarters while his staff 

frantically tried to discover the source of the leak." 

By 11 June all of the principals had been interviewed. Those aboard the Barnett were 

interviewed more than once. Out of this work emerged a very unpleasant picture of official 

neglect and confusion concerning the safeguarding of communications intelligence both on 

the Barnett and in the newspapers. Because of the perception that newsmen 

accompanying U.S. forces were sworn to secrecy, indictments of the principaI employees of 

the Chicago Tribum were sought on 9 June, even More the inquiries were completed. 

They were returned on 7 July by a Chicago grand jury. At this point serious snags 

appeared at every turn, and the matter lay in the hands of the grand jury and a special 

prosecutor for several weeks while the navy added depositions to a record that increasingly 

showed that Johnston, a British subject, had, with the help or negligence of others, 

betrayed the trust placed in him. 

While many in the navy focused on fmding a suitable punishment for Johnston, 

COMINCH issued another memorandum on 20 June 1942 similar to those he had originated 

in March and April. It was sent to CINCLANT, CMCPAC, and CDR- SWPACFORCE bearing the 

subject "Control of Dissemination and Use of Radio Intelligence." Within the navy this 

would prove to be the only remedial action to come out of the Johnston case.178 

On 24 June the New York newspaper PM published a story without attribution 

announcing that the Justice Department did not plan to prosecute anyone, either in the 

newspapers or in the U.S. Navy,lW as 8 result of their role in the revelations. Ironically, 

three days later the navy discovered that Johnston's own government had earlier declared 

him "unreliable" as a c~rrespondent.~~ It was the same government, however, that 

subsequently forged the ultimate solution by addressing the correlation between the 

Johnston revelations and safeguarding communications intelligen~e.'~' 
On 14 July, the special prosecutor, Mr. Wifiam D. Mikhell, transmitted his 

comprehensive mrt on the ChieQgo Tribune CaseA to Attorney General Fh Biddle 

and Secretary of the Navy Frank Knox. His conclusion, aRsr he had reviewed the Iaw, the 

evidence, and the cbcmsbces surrounding the "leak,* ended by suggesting that "tbe 

game may not be worth the candleA and that the-national &ort would be better served if 

the case weredroppxLm 

In the mind of the special pwcuhr, noae d his major reasom for droppii the mse 

concerned the safeguarding of mmmudcatiow intelligence. Three salient pqints 

concerning the merits of the government's case were cited instead. MI were related to the 

personal behavior of the principals: "1) Johnston said bn 8 June) that he got the 

infomation from a paper he found on his desk; 2) Two &ws testified seeing Seligman 

wurking at a ale in his quartms and that Wbre him was a biting on Navy paw? 

giving a list d dap veaela divided into a 'striking force, support force, ete.'; 3) If, as 

am likely, some offar feR a mpy of that dispatch lying around, it may fairly be said 

there was as much carelesmes on the ship as the Tribune was guilty of, and the Jury may 

think so. "= 

No further action was hken until 15 Auht 1942, when the British Admiralty 

delegation in Wadhgbn mt a letter to Admiral King expressing concern that the 

Hearst rev&tiotls posed a danger to sp&l inteiligeme mew, that a trial would 

further compromise this source, and that "preservation of this invaluable weapon 

outweighs almost any other consideration" King's reply reassured the British that the 

U.S. Navy would not do anything to increase the harm already inflicted by the original 

news shy.m Five days later, the Chicago Daily Tribm carried the front story, 

W.S. Jury Clears Tribune." This story signaled the end of the grand jury investigation, 

tbongh no masons were ever given to the press by Mr. Mitchell, the special prosecutor. 

what were the fkc& in the strange case ofstanley Johnston? As noted above, CWCPAC 

3112212 May 42, was the message that passed G~NCPAC's final appreciation of the 

Japanese order of battle for the Battle of Midway to the commanders of Task Forces 16 and 

17, Admirals Spruance and Fletcher, respectively. The message was passed in 

mmmunkations channels available to other ship. Contrary to normal practices, which 

expcted oomm~tors to ignore traffic not addressed b their ship or coder, it ww 

probably decoded by communications officers from the kingdon en mute home hm the 

loss of their ship at Coral Sea, who were acting as wakh shnders aboard the hmport 

USS Barnett (AP11). Their reason for doing so may have been the presence of the 

Lexington's exmtive officer, Co~nder Morton Seligman. The message was given to 

Commander Seligman, who, apparently under the impression that he was authorized to do 

80, shod the message to Johnston, who had been a- the Lwangton during the bade 

and was be@ evacuated with the crew. Johnshn and Seligman may have shard the 

same quark= a- the Bun~tr.~ 

On 7 June 1942, five dap after Johnston's arrival in San Diego and one day after 

CINCPAC's "POA Communique #3" appeared announcing "a momentous U . S. victory, " 

Johnston's story of U.S. foreknowledge of Japanese forces and their plans appeared in the 
Cwo Tribune d othw newspapem in Washington and New Yortm The headlines 

that introduced the story on page 4A in the Wwhingfon Times Herald for 7 June 1942 

revealed without a doubt that the author had been privy to secret material concerning 

daplleq intentiom and strategy: "U.S KNEW ALL ABOUT JAP FLEET, GUESSED THERE 

WOUU~AFTJNTAT ONE IMSE,REALATTACKAT AN~HER" 

Though be could not know the extent ofthe duplicity involved, WalterWmchell, in his 

column in the New York Wy Mirror, characterized the Tribune as having "tossed 

security out the Adow." Understandably, Johnston's repeated denials that he had ever 

seen CINCPAC'S message were received with cynical disbelief in Washington. Even his 

media superiors readily admitted they could not otherwise account for the ~imilarities.'~ 

On 8 June, following an inconclusive meeting btween high naval and newspaper 

OECAS, Jo-n and his editor in Washington, Arthur Henring, met privately with Vice 

Admiral Russell Wdlson, Admiral King's chief of staff. It was during this meetingp as 

noted by the special prosecutor, that Johnstun may have contradicted himself (Admiral 

Willson was to say that Johnstan "confessed") and admitted seeing a list of Japanese 

vehlseIs.- With the ooncurrence of the secretary of the navy and the president, Admiral 

King barred Seligman from promotion fd'rever. Ssligman retired in 1944.1so 

OP-2o.G'~ -&of the damage done by the theohuston revelations took a long time 

to develop primarily because the Japanese themselves were slow to change their 

pmdures. Ned~Iess, OP-20-G maintained it was n6 me= coincidence that within a 

few weeks of the Johnston expod drastic changes were made in virtually all Japanese 

codes and ciphers including the Japanese Fleet General-Purpose System, which changed 

on 15 August, only two months into the current cipher. Con&tent with these changes, 

navy monitors ah noted the omission of message serial numbers beginning on 15 August 

and a mqjm chqge in the Japanese dbii system on 1 October 1942." 

All of the Japanese refinements were justifiably described by OP-20-G analysts as 

serious threats to their capability to produce current intelligen~e.~ Thus, it is difficult to 

say at this point that a single event occurred that prompted Admiral King to decide what 

course of action he would hke. It may have been OP-2bG's concern that a jury trial would 

have even more painful consequences than those already experienced, or Admiral 

Wbn's reading of the meeting he had had with Jobston, or the trauma of preparing 

highly classSed testimony to be given Wore a Chicago grand jury. Clearly, Admid 

King had decided not to implement the 7 July grad jury indictment when he responded to 

the British letter in August; and the evidence suggests, albeit weakly, that as early as 20 

June he had begun to regret even seeking the indictment. 

Throughout the Johnston affair, OP-20-G consistently sought a plausible cover story 

to minhh the damage already done. They appded to King for future safeguards to 

prevent the loss afa vital advantage to the navy. King's reiteration of his restrictions on 

distribution on 20 June, while perhaps not all that OP-20-G wanted, strongly suggesbd 

that these appeals were heard. lgg 
Questions concerning the appropriate applications of communications intelligence to 

wartime emergencies of a11 types continued to arise. One problem addressed in December 

1942 affected how newspapermen and radio broadcasters treated information they knew 

originated from enemy communications. A new paragraph was prepared for insertion in 

the *Code of Wartime Practices for the American Press" by the secretaries of war and navy 

and sent to the director of censorship for implementation: 

ENEMY COMMUNICATIONS 

To the end that the enemy may not have information concerning any succegs the US- may attain 

in deciphering his encoded or enciphered communications, no mention should be made of 

available or captured enemy codes or enemy ciphers, or about the intelligence gained from 

intercepting and studying enemy redio messages. 

A prestigious trade journal gave immediate approval to the addition while at the same 

time registering the idea that after the war censorship should not continue. After citing a 

post-Pearl Harbor report that "monstrously exaggerated" U.S. losses as an example of 

irresponsible behavior, the editorial concluded with some ideas that are still relevant: 

As between an ethical professional requirement that a journalist hold nothing back and a 

patriotic duty notb shoot one's own soldiers in the back, we have found no dificdty in melting a 

choice. Freedom of the press does not carry with it a general license to reveal our secret strengths 

and weaknesses to the enerny.ls4 

It was not until 1985 that anyone from the Pac&c GOMINT centers received any formal 

recognition for his contribution to either the Coral Sea or Midway victories. In 1985, in 

response to a massive outpouring of affection from his friends, Joseph Rochefort received 

the Distinguished Service Medal posthumously from the secretary of the navy. For the 

rest, their epitaph was most fittingly expressed by a perfect stranger many years later: 

Aiary, with its flickering lamp, stumbles along the trail of the past, trying to reconstruct ita 

scenes. to revive ita echoes, and kindle with pale gleams the passion of former days. What is the 

worth of all this? The only guide to man is his conscience. The only shield to his memory ia the 

rectitude and sincerity of his actions. It is very imprudent t~ walk through life without this 

shield, because we are so oRen mocked by the failure of our hopes and the upsetting of our 

cakulations, but with this shield, however the f~tes may play, we march always in the ranks of 

h~nour.'~ 
1. Hattari, Vol. XI. 181, recorded that Admiral Yamamota had initially hued an order on 5 November 1941. 

directinghat Midway be capturedduringthe second phaseof thew. 

2. Morhn, VoL III, 58; Willmott. 116. 

4. Morhn, Vol. 111, 59; Fuchida, 66-71. 76; Willmott, &9, 16+33. W.illmo# recud pawage of the Nad 

Expansion Act indune 1940; Morison recod the Two-Ocean Navy Act in July 1940. The first hill authorized an 

expanaionof 11 percent. Tbe second bill euthorized a 70 percent increase. Reax Admiral ddius A~UB hr, 

USN {ret), Adminiskation of tl Nw Deprtmenb in WWIZ (W~&~JI@O~, 1459). 57. 

6. Hatbri, VoL II, 132. 

7. Hattori, Val. 11,128. 

8. Fuchida, 48: Hattori. Vol. 11,133. 

9. Fnchida, 7844. 

10. Fuchida, 91-3; Moripon, VoL IV, 1-75. 

11. Fuchida. 72.95. 

12. SRMNO1ZL ad H, 2,4,and 5March 1942, f tC45,N~. 

13. $RMNO12I and L, RG457 NA, 11 March 1942. 

14. Dyer, 255. .>? 

15. SRH272, -7 NA. 

16. Com 14 1407002, CINCPAC message file, RGa8,NA andSRMNOf 2&, RW7, NA,each 14 May 1942- 

17. HC IV W.3.25.16 May 1942,lettsr from Redman to Murphy. 

18. CMCPAC 1301312, CINCPAC mewe files, RGS8,NA. 

19. Fuchida, 120. 

20. SRH012,Q March, andSRNMOl23,0126,23 March 1942. AllRG457 NA. 

21. SRNMOQ73/B, 17 April 1942; SRMNOOS; and SRNEAQ697,24 ApriI 42. All RG457, NA. 

22. SRHl8O and SRH2Q7, both RG457, NA. 

23. Lstter of23 April 1942 to War PIaas.HC IV W 111.25. 

24. SRNM0643,066#, and 0673; endSRNS 1517 (slid27 April 1942),andallKG457 NA. 

25. SRMNOIZL, 27 April 1942, W7 MA. 

26. SRNS 1517.1 May 1942, RG457, NA; Corn 14 01 11082, May 1942, CINCPAC message fi3e, RG38, NA. 

27. SRHO12,2 May 1942, Ii-7, NA. 

28. Morison, IV, 88. 

30. ~OlZM,S~272/H, 8 May 1942,botb W7, NA. 

31. SRNS 151 7.9May 1942, RC467, NA. 

32. SRMNOl2L,SRH2721H,Q May 1942;RG467,NA. 

33. COMINCH 1219452 May 1942,CINCPAC measagefi, RG38,NA. 

84. SRNS1517,13 May 1942,RG457, NA. 

35. SRMNOO~,OP-~OG &sage dated 15 May; SRMNOlm, rn-gea trdated and pobliahed 14-20 Mag. A11 

RG457, NA. See aLso OPNAV 151 7452, CINCPAC message fde, -8, NA. 

36. SRMNOI2fH. SRNS1517,13 May 1942, RG457, HA. 

37. COMINCH 14152'7 May, found in NimitzCommartd Summary entry for this date. HCIVWII 2.2. 

38. SRMNOIWL, 14 May 1942, RG457, MA. 

38. 140639, May Nimitz CommandSummary . 

40. Morison, Vol. IV, 80; COMINCH 1415272, May 1942, CINCPAC memage file, RG38. NA. 
41. m-7. 

42. M, 19-80; and hybn inbrviaw, 221-24 and23142. 

43. COMGENHAWDEPI' h CENCPAC 2519802 May 1942, CINCPAC mge file, -8, NA. 

44. Wr, 101. 

45. Ni Command bnmaq, H May 194% mrnpured to COHINCH 1415872 'May 1943 in the oame 

&mmmk FotePiderraofboa-HaddMe-eontheJawWCHidwag,-h 

1219452 May 1942, Nimk snmmary, IiCIVWIIS2- Ses dm SFtMMOlBRI and !StNS 1517, both IS 

~Y,~SRMPTO~~I~~~~~,~~~,NA. 

48. CO~CHtoCrPJCPAC,15%1302MsylW,PT~CommarPdS~,Bwkl,HCI~2I 

47. Ibid. 

88. Murieon,V01. IV, 00. 

49. CINCPAC 160M'TZ to CTFI6,CTNCPAC Message tile, RG38,NA 

50. .NimitrCod &ImmarJr, 16 mbay 1942. HC IV W II9A 

51. Ibid 

52. CINCPAC 1808862 May 1918, NirnitP m, Bmk l$rCIVWIlSS and CPfCPAC 

&, RG88, NA. 

63. COMINCH b CINCPAC, 17mZ May 1942, Nimitz Command Summary, Bwk 1, HCIW.2.2. 

54. COMINCH 1722222 May 1942, NMia CummatadSummary. Ebk 1 ,HCIVWIISS. 

65. SICPFS1617,18 May 1WZ. -7, NA 

56. Cam 14 18L~IYap;Cwnl4tpCOllBB080984Zd~l~,aIlCMCPAC~fae,~NA;XtZH~2, 

18Mayl942,dSRNS1SL7,18~lsa8, Wm7,NA. 

51. CINCPAC 1- 1-572 ad 1821d52 May 1442, -ely; Nimih P-, Boot 1, 

HCNWU3 and CINCPAC file, -8, NA. CTF 16 was oriqinallg ordemd ta retarn ta Had aRcr 

Hahey wan sighted by Admiral buye's pakols. CINCPAC 1600232 BdPy to All TF Cmdrs Pac, d Corn 14 

1523162 tp COM3 mikt Japaneaa reactions; CMCPAC to CTFl6 1608072 May 1942. AU memagen are in the 

CINCPAC fk RG38, NA 

58. Radio Inklligeace Passed Outaide OP-a0.G. HC W WA2& ad SRMN005, RG46'7, HA 

60. slleh~eo~~tionunbeinBarredfmrn~2OMay 104ZhMertoOP-aO-CI~by hmmaderG. W. 

hishy in SlWNW5, R-7, HA. 

61. Ibid. 

6%. Lord, 21; Morieon, Vol. IV, 181-168; both addre= thii h, a J the dwa albrnutiw ideutities are seen 

in tbe formal aad~~~e iQHCI~d~Oo6,~7..NA. 

63. laytan, 4214. 

a. -to corn 2122452 w, cmcp~c a RGS~, NA; SELNS ISIT, 8% ~.y BG 457, 

NA ~q~eaetcsnba&dinHCIVWVn.lB. ~arddthigtettwWahb~fnSRHO12, 

Vd IdSEMN005, W.NA. 
65. Corn 14 to COMB 2207922, CINCPAC mew@ file, RG38, NA; See aleo Laybn, 41 -22; and Remkiacencaa, 

HCXV W XI, in which Rochefort nobd that Hypo wan very impatient with tho= who would not ampt the 

definition of AF a% Midway, parLicularly when they had the same information 

Admiral Turner was relieved as Chief of War Hans on or about 25 May 1942. He was hter given command of 

an amphibious force that subsequently assaultsd Guadalcnnal. His relief on the we d a great naval battle is 

difficult to explain in a witive context. particularly in light of his tense relationshiper with the Navy's 

Comtuunieations Dimrate and others and his apparent isolatjon from Admiral King. There is aome confusion 

over wben his relief actually occurred. Hb biographer, Dyer (263) said 25 May, but SRMN006 (RG467, NA), a 

colkctiorr of papers related to Midway, contains a situation report signed by Turner dated 29 May. Larrabee 

r201, indicated reaaons outaide the navy for his diamiaRaL AEcOrding b Larrabee, he wma removed nt the 

insistence d General George C. Madall, COS U.S. Army. h March 1942, acowding to kabee, General 

Marsball convinced the president that Turner, as a member of tbe Joint Planning Staff, was tm difficnlt to work 

with. hrabee (1 90) also maeM that in 1942 King shiRed Pa&= war planning functions to Nimitz after 

Turner was relieved. 

66. Corn 14 to COMB 1903662; Belconnen to COMB 1908402, COM 14 b COMB 1909482; Belconnen to COMB 

I91610Z;all May 1942 and all inCfNCPAC mewagefde,RCr38,WA, SRH272,lS May 4~SRMNOl%M,a0 May 

42; SRMNOlZ/X&L, 21 May 1M2; and SWS 1527.21 May 1942, all RG457, Nk and CINCPAC OPPlan 2942, 

20 May 1942,"Swey dOpposing&mngthsP HCIVPWIl.18. 

67. CMCPAC to CTG2.1,2223#2 May 1194; CINCPAC 2302352, Maj 194%; bath in CINCPAC mmge fi, 

RG38, Nk, M-, Vol. IV, 166 and 170; Willmott, 337, Lundstrom, 175. For Nimih' estimates and the 

influence of COMINT, see Corn 14 2319222 May 1942, CMCPAC message file, RG38, NA, SRMNOl2/L 24 May 

1942, RG47, NA: Nimih' Command Summary 23 May 1942, HCNWII.23; SRHOIB, 23 May 1942, RW7, NA; 

CINCPAC Bulktin 174,280057Z May 1042; CINCFAC to CTF8,8802452 May 1942 and 2821532 May 1942,all 

in CINCPAC mesaage file, RG38, NA. For Theobald's treatment of COMINT, see CTF8 "Estimate of the 

Situation: paragraph 14, found in U.S. Navy War College Study of Midway, HCIV W VII 6. 

68. SRNS 1517,21 May 1942,RG467, MA. 

69. Negat predickd the impending departure of this fleefa two battleship divigians, 1 and 8, from Kure in a 

measage on the 21 4 but the sigriicance of this information was not ernphasiaed. OPNAV 21 16392 to CINCPAC 

and COMSWPACFOR, CINCPAC meage file, RGS8, NA; Hoyt (286) discuses the role of Yamamou and the 

Main Body during this campaign, as do Morison and Fuchidrt. 

70. CINCPAC 2201352, CINCPAC mwa$s file, RGS8, NA. 

71. CINCPAC 2202192, CINCPAC m-ge fde, RG38, NA. 

72. COMSOWESPAC 23M25Z May 1942, CMCPAC me- file, RC38, NA. 

73, Corn 142203382 May 1942toCOMB.CINCPAC rneasagef&,RG58,NA. 

74. COM~ WESPAC 2405492, CINCPAC message file, RG38, MA. 

75. COMINCH to Spenavo tondon, 1812552 May 1942, info COMSOWESPACFOR and CINCPAC, CINCPAC 

message file. RG38, HA. 

76. Potter, 8% WiBmott,342. 

77. Instructions for the Tangier can be found in 2805832, May 1942 CINCPAC to the Tangier and 

COMSOWESPAC, CINCPAC marreage He. 

78. Fuchida, 130-33. 

79. SRNS 1517,24May 1942.RW7,NA 

80. SRHO12,24M8p 1942,RG457,PIA;Com 14toCOAdlB252126ZMay 42,CINCPACm~agefle. 

81. CINCPAC~CTFs4,9,l~,l6,0223192duoe 1942,CINCPACm=gefle,RC;38,NA. 

82. The date of the &very can be inferred in Pothr (82) when he described a meeting on 25 May between 

Nimitz and Rochefort to which the lamr arrived late and in a disheveled condition ostensibly becaw he t~as 

waihng for the cipher dolution. This is probably the same meeting Layton places on the 26th. In Corn 14 ia 

COMB, 2721182 and !&'!Z1682 May 1942, the midon was shared with other COMB add- (CINCPAC 

message file. RGS8. NA). It would have been unusual for one center to withhold impottant idonnation fbr two 

days83. Laybn, &-28; #m 14b COMB W20582 May 1942, CINCPAC mmge file. RG38, HA. 

84. Potter, 82,83,87. 
85. SRNS 1617.25 May 1942, RG467,Nk 

86. CINCPAC to COmCH 2702092 May 1942, CINCPAC mmaage fils, RC38, NA. 

87. CTP7 to Gudgeon, 2600152. May 1942; CINCPAC mezaage file, EU;38, NA 

88. CINCPAC 2603452, CINCPAC measage fde. 

89. Corn I4 to COMB 2622442 May 42, CINCPAC memage Pile, W8, NA. 

90. Lundakom, 171. 

91. Morimn, Vol. IV, 81. 

92, OPNAV to COMB 2622aDZ May 1942, CINCPAC me file, RG38, Nb, See also Belmnnen to COMB 

2804282, May 1942, in m file. 

98. SRMNOlPH, 27 Mny 1942, -7, Nh 

94. Corn 14 2800402, May 1942, CINCPAC mes~ag~fle,RG38, MA. 

95. Corn 14 toCOMB 2820202May 1942;OPNAVtoC0~2816502May42,CLNCPACme~file,RG38,NA. 

96. SRNS 1517,28 May 1942W57, NA, Corn 14 to COMB 2820092 May 1942, CINCPAC memags fde, RG38, 

NA; andSRHOl2, RG457, NA,game day. 

97. Corn 14 2831322. May 1942, CINCPAC message file, RG58. NA. 

98. CINCPAC Bulletin 74,2800572 May 42, CINCPAC message file, RG38, MA. 

99. SeeCINCPACwCTF3 SO2452 and 28215aZMay42,CINCPACm~afile, RC38,Nk 

101. Deployment of forces from Marison, Vol. IV, 170: arrival of Mald in Alaska from Nimitz Command 

Summary, HCTVWII.22, May 22 when he departed fmrn Hawaii 

102. OPrJAV t4 COME 2920452 May 2942, CINCPAC message Ale, RG38, Nk 

103. OPNAV tp COMB 2906152 May 1942, CINCPAC m~ge fil. RG38, NA. 

104. Corn 14 to COMB 2902 142,2902162 and 291 1422 May 1942, CINCPAC me- fh. RG38. NA. Corregidur 

ended operation on 6 May 1942. 

105. Corn 14 to COMB, 2920082 May 1942, CINCPAC message file, RC38, NA. 

106. Bulietin Number 75. CINCPAC 29023 f Z May 1942, CLNCPAC me-- fde, RG38, NA. 

107. CINCPAC to COMNCH !4904192 May 1942 and CINCPAC to all TF8 2914092 May 1942, both CINCPAC 

m-ge file, RG38. NA. 

108. Corn 14 to COMB 2922262 May 1942, CINCPAC message file. RG58, MA. 

109. Corn 14 to COMB 2922342 May 1942, CINCPAC message file. RG38, NA. 

11 0. CINCPACbCTF8292029Z May 1942,CINCPAC message file, RNB, NA. 

111. CINCPAC 2821512 Mey 1942. CINCPAC mesaage file, RC138, NA. 

112.2821 232 May 1942, CINCPAC message file, RG38, Nk 

113. 2916212May 1942,CINCPAC mmsagefde,RG38, NA. 

114. COMNORWESSEAFRQN to CTF8 3 114292 May 1942. CINCPAC mewge file, RG38, NA. 

115.2920022 May 1942, CINCPAC me-@ file, W8. HA. 

116. Fuchida. 119. 

117. Ibid., f 22. 

118. Ibid.. 11s. 

119, hid., 128-24. 

120. Ibid.. 119-120, Deployment of TI? 17 under Admid Rank Jack Fleaer, was ordered for 1830 Iocd time 

30 May 1942 inClNCPAC290206ZMay 1942,CINCPAC mmge file, RG38,NA. 

121. CINCPAC %Order 2942, 27 May 1942, gave the Japanese rendemow point at 27N, 17OE. See also 

CINCPAC to CTF 16,30Oaa?Z May 1942; and CINCPAC Bnlletin Number 'lbsent to all TF Cmdrs, etc, 3002412 

May 1842, all CINCPAC message file, RG38, NA. 
122. Belconnen to COMB 3004402 May 1942, CINCPAC message file, RW, Nk 

123. Operatiom Ph 29-42 pubIished on 2 Jm. CINCPAC to CTFs 4,9,17,16,0223192, June 1942, CINCPAC 

mmge file, RG38, NA. 

124. OPNAV tuCOMB 3020252, May 1942, CINCPAC rneaaage file, RG38, NA. 

125. Corn 14to COMB 31054.52, May 1942, CINCPACmpfile,RG38,NA. 

126. Corn 14ta COMB 3109342, May 1942, CINCPAC mesaage file, RW8, NA. 

127. Corn 14ta COMB 3121542, May 1942, CINCPAC message file, RG38, NA. 

128. COMAmC to CINCPAC,CTFS 0221302,CINCPAC megsage file. RG38,NA. 

129. CINCPAC to CTFs, etc., 0203472, CINCPAC message file, RG38, NA. 

190. DubzhHarhor bCTF 8.0214302 June 1942.CINCPhC messagefih. RG38, NA. 

13 I. Corn 14 to COMB 0200242 June 1942. CINCPAC message file, RG38, NA. 

132. Corn I4 to COMB 0200242 Juae 1942 and Belwnnen 0203352,0204262 and 020630Z dune 1942, all 

CINCPAC rnegsage file, RGSB, NA. 

133. Ibid. 

134. Ibid. 

135. Morkn, Vol. IV,see map aRer p.94. 

136. OPNAV b CINCPAC, eic., 02223 1 Z June 42, CINCPAC message fde, RG38, NA. 

137. CINCPAC to A11 CTFs, 0316372; CINCPAC to Midway, information to all CTFs 0318552, repeated 

0319272; CO~0WESl%AFRON to CLNCPAC, COMINCH 031941Z; NAS Dutch Harbor b CTFB. Corn 

Akkan Seaor, Caaw 0322152 andtoCTF8,0400302;all June42,aU CDICPAC message file, RG38, NA. 

138. Midway to CINCPAC, 0321352, June 1942. CINCPAC measage fde, RG38. NA. 

139. CINCPAC to CTFs, info COMINCH and COWGENHAWDEPT 0821532, June 1942, CINCPAC message 

fde, RG38, NA. 

140. CIPJCPAC to CTFs, info COMINCH, 0322072 and 0400L7Zdune 1942, CINCPAC mewge frle, RG38, NA. 

141. CINCPAC OdOlOlZ June 1942, CIHCPAC measage me, RG38, NA. Daylight in Hawaii in June occurs 

roughly hetween 17002 and 05002. AIlowing for Daylight Saving Time, i.e.. War Time, there would have been a 

twelve- i-adof an eleven-hour daerence between GMT and the time at Midway and an eleven-hour difference 

in Hawaii. 

142. Corn 14tuCOMB 0300462June 1942,CMCPAC mwagefile,RG38, NA. 

143. Ibid. See also CINCPAC message file, RG38, NA, 0300472 June 1942. 

144. CINCPAC to Midway, CTFs 4,7,9,16,17 0303252, June 1942, CINCPAC message file and CTF 7 to TF 7 

0306192 June 1942, CINCPAC mege file, RC38,NA. 

145. CINCPAC me-ge fde, RG38, NA,0408012 June 1942 (032301W June 19421. 

146. OPNAVKOMINCH to COMB Adees, 0420002 June 1942, CINCPAC mamgefh, RG38, NA. 

147. CINCPAC to all CTFs 0410352,June 1942,CINCPAC message a%. RG38,NA. 

148. CINCPAC 0418092 June 194210609 on Midway, 0709 in Hawaii. CINPAC mge file, RG38, NA, An 

18042 sighting report gave the distance from Midway as 180 miles. CINCPAC mezsage file RG38, NA, 0418572 

June 1942. 

149. CINCPAC tu COMWESTSEAFRON, COMNORWESrSEAFRON, COMGENHAWDEPT 04LB57Z June 42, 

CINCPAC message file, RG38, Nk 

150. Fuehida, 86; Willmott, 343, and Moriaon, Vol. IV, 84. 

151. SRMNOlBH,4 June 1942,RG457,NA. 

152. Corn 14 tu COMB 0421362 June 1942; CINCPAC to Ws 11,16,17,0423492;Cvm 14toCOMB0423582;Com 

14 ta NAVAIRSTA Midway 050059~041459HWT]; and CINCPAC to CTF 16, CTF 17,0502332 [041733HWTl 

dl June 1942 and aU CINCPAC measage file, RG38, NA. 

153. See, for example, CINCPAC to Midway 0423402 [1440HWTI; CINCPAC to all CTFs 0500452 [041545HWTI, 

all June 1942 and all CINCPAC mesgage file, RG38, NA. 
154. See CTF 16 to CINCPAC OM1204Z June 1942 [I604 MWT, 4 June 19421; CJNCPAC to ?didway 0603962 June 

1942 [I835 HWT, 4 dune 19421 an* CINCPAC to all CTFs COMGENHAmEPT, COACINCH, and 

COMSOUPAC 0605652 June 194a [1856HWT, 4 June 19421, all in CINCPAC !&, RC38, MA. 

155. SEWN01 WH, 6 June 1942, RG457, PTA. 

156. SRNSlfi17,6 June 1942, RG457, NA. 

157. CINCPAC messagefile,RG38,NA,0519162 [Olil015WI June 1942. 

158. Morimn, Vol. IV, 178-79. 

159. Morison, VoL IV, 179, debbes how Admiral Nirnitz was kapt abreast ofdevehpmenta by them reports. 

160. SRhMOlaRIGJune 1942,RG457,NA. 

161. Willmot& 508. 

162. CINCPAC War Diaty, 6 dune 1942,ONI Review, May 1947. 

163. Bw11, 148-41. 

164. SUNS15 17/RI, 7 June 1942, RUT, NA. 

165. SRMNOlWH7 June 1942, RW7, MA. 

166. SRMNOfZ/L,7June 1942,RG457,NA. 

167. CINCPAC War Diary, 7 June 1942,ONI &view, May 1947 ad Willmort, 510. 

168. WSL51I!RI,8June 1942;SRMN012/H,8 June 1942,both RG467,NA. 

169. SRMNO12L,8June I942,RG457,NA. 

170. SRMNOlZ/H, 8 June 1942, RG457, NA. 

171. Potter. 

172. Fabian interview, NSA Om1 History, OH 09-88 

173. SRH 289,W7,NA. 

174. CINCPAC170335Z May 1942, CINCPAC massags file. 

175. CINCPAC to COMINCH 0320432 June 1942, CINCPAC measage file. 

176. HC IV W 11 2.2 CINCPAC's message of 31 122 1 May wtltained his fd appreciation of the Japanass order of 

baMe prior to the Battle of Midway. 

177. Ibid. 

178. SRH012. Vol. I1 and accretion to Vol. 11, RG457, Nk 

179. HC IV W VII.2. 

180. &id. 

181. bid. 

182. HC IV W VIIS. HereaRer, Mi-Ll report. (U) 

183. Ibid 

184. mid. 

185. Mitchell report. 

I#. Potter. 8%. 103, ad SRH012, VoL I1 and accretion to VoL IT, sbow several points of view concerning the 

situation on the Barnett. T& characterization of the role of Commander Seligman is also based on the 

eyewitness account of Rear Admiral Robert E. Diron. As CO of the Leringbn's SeoutBomber Squadron 

Lieutenant Commander Dimn told the FBI on 8 or 9 June 1942 that he bad witnessed Johnston taking extaoaiw 

noks from CMCPAC's 3 1 May 1942 mew. Robert Mwn, Eyewihesrs, US. Naval Institute Pnrceedlnp, June 

1982,4045.) 

187. HCIVW vIr.2. 

188. Nu York My Mirror, 7 July 1942, ad Mitchell report. 

189, HC. IV W ViU. 

190, Masan, EyewihPesa 

191. SRHOl2, VoL If, Chapter V, 286, and Appendix, 392,RG457, NA. 
192. Ibid. 

193. SRHOiZ VoL I1 W'I,NA. 

194. Whky-&bn Amsn'ean Wr, 112/W42. These quotatiom are aho in WHO12 Vol. 11, Chap. V, 28S91. The 

WhukpRaton Amhn Le&r was a businemoriented newdettsr published by a company founded in 1918 by 

Hunhg-hn Wh&y.Dallas Magmine, Madarch 1986, NEXUS Databatw. 

195. Job Colville, Fringes of Power: 10 Downing Street Diaries 1939-1955, New York W.W. Norton and Co., 

rm. 
BIBLIOGRAPHY 

Part One 

Primary Sources 

1. Wrd Group 457 (RG457) National Archives INA) 

a. SRH012,' The Role of Radio Intelligence in the American Japanese Naval War 

August I941 June 1942. 

b. SRH180, U.S. Naval Pre-WorId War XI Activities in the Philippine Islands 1931- 

1942. 

c. W207, Evacuation of USN COm Personnel from Corre@dor in World War IT. 

d. SRH235, Contributions to Submarine Warfare. 

e. SRH264, Wenger Lecture to Naval War College. 

f. SRH288, Redman Correspondence. 

g. SRH272, CINCPAC Enemy ~ctiviiiies File. 

h. SRH278, Hypo War I)lary 1942. 

i. SRH279, Communications Intelligence Organization 19421946. 

j. SRH289, Mobile Rl Unit Activities. 

k. SRH313, Mobile RI Units with TF16,l-24 May 1942. 

1. SRMDOO9, JICPOA Administrative Files January 1942September 1945. 

m. SRMN004, ClNCPAC Intelligence Bulletins, 16 March-1 June 1942. 

n. SRMN005, File of Memoranda and Reports Relating to the Battle of Midway, the 

"K" Campaign, and the Aleutian Operation. 

o. SRMN008, CINCPAC Combat Intelligence Bulletinsand Radio Digests, 1 March31 December 1942. 

p. SRMN012, Corn 14 Tn Summaries and Fleet Intelligence Summaries prepared by 

Hypo and Layton, respectively. Frequently Layton's contribution was embellished 

by acomment fromCINCPAC War Plans. 16 July 1941-30 June 1942. 

q. SRMN013, CINCPAC Intelligence Bulletins, I June 1942-23 September 1945 

r, SFLbWO15, The Establishment of Advanced Intelligence Centers, May 1942- 

August 1943. 

s. SRNM001-045 1, Messages intercepted, decoded, deciphered, and translated by 

Hypo and Melbourne with comments by OP-20-GI. Some translations are also by 

OP-20-GZ; 13 March-15 April 1942. 
t. SRNM0452-0952, Messages from the period 16 April-9 May 1942, from Hypo, 

Station C, Melbourne, and OP-20-GY. 

u. SRNMO953- 1 141, Daily Summaries and Translations 9-18 May 1942. 

v. SRNM1142-1292, Translations from the British base at Colombo and from the 

Admiralty concerning Japanese Navy activity in the Indian Ocean, Bay of Bengal, 

and the Pac=c west of the Marshalls between 21 January and 5 June 1942. 

w, SRNS0001-0078, Summaries prepared by UP-16-F-2 (ONI) based on COMINT 

reports of Japanese Navy activities 14 April30 June 1942. 

x. SRNS 1290-1458, Summaries of Japanese naval dispositions and intentions 1942- 

1945. 

y. SRNS1459-1516, TrafEc Intelligence [T/AJ summaries of Japanese Naval Forces, 

1942-1 94-6. 

z. SRNS1517, Daily TI and CI [translations] summaries from Melbourne 20 March4 

June 1942. 

aa. SRNS1518, Operational and Administrative messages from Melbourne, March 

1942-March 1944. 

2. Unit Histories 

a. History of OP-20-GT-P (Truffic Analysis-Pacific]. OP-20-GT-P was estabLished in 

March 1942. Prior tu that time no traf5c analysis was conducted in OP-204. 

From 1 March to 10 April 1942, traffic from Hypo was sent to OP-20-G via air maiI. 

Tr&c from Bainbridge, Washington was sent by teletype. History Collection 

IVWl.5.8. This history is classified TS. 

b. History of OP-20-GYP-1 {Cryp&znalysis-Pacifi}. This history was written after 

the war, probably by Stuart McClinbck. It concerns the activities of the PacZc 

cryptanalysis unit in Washington. It contains information concerning the steps 

leading to success against the Japanese Navy General-Purpose Code, JN 25. 

History Collection IV W 1.5.12 and 5.13. This history is classified TS. 

c. History of OP-20-GI-P (Combat Intelligence Pucific). History Collection IVW 1.5.3 

This history is classified. 

3. Record Group 38, National Archives 

a. CINCPAC message files. This file contains the daily classified messages 

originated by headquarters CINCPAC for the period covered by this chapter. 

b. Distribution of Intelligence by ON[, Box 8-ZIEF28(298). A March 13 1942 

memorandum from OP-16 (ON11 to COMIMCH responded to a message from 
CINCPAC (Originated by Corn 14) pertaining to duplication in reporting and lack 

of security. As a result, OP-16 discontinued its daily bulletin. 

c. ON1 Intelligence Reprts, Box A8-21EF{294) Folder A&mF January-April 42. 

This folder contains out-of-date reports of sightings of Japanese ships by American 

submarines at a time when much more accurate and timely reports were available 

in COMINT reprts from the Pacific centers. An ON1 Japanese Navy Order of Battle 

is in the prewar format. It does not reflect the current organizational structure, 

improperly showing carriers in the numbered fleets instead of in the First Air 

Fleet and- Carrier Strike Forces. 

d. Records of Headquarters COMINCH, Box AS-2, Folder 1: This box contains 

several items dated February 1942 that reflect ONI's efforts to produce 

intelligence reparts from non-GOMINT sources such as the news media and State 

Department reports. 

e. Coral Sea, A British View. A Report of 22 May 1942 from Chief of Intelligence 

William Donovan to Secretary of the Navy Frank Knox. Box ASZtEF(296). 

4. CNO Summaries of Japanese Naval Activities 14 April40 June 1942, White House 

Map Room copies of ONI-prepared daily reports. Unintentionally, they reveal differences 

of opinion between ONI, Hypo, and OP-20-G. 

5. Rudolph J. Fabian, Commander, USN (ret), OIC Melbourne RI center: On 10 and 12 

August 1942, Fabian and other officers and men in the RE center in Melbourne were 

recommended for recognition by Washington (Fabian for a Distinguished Service Medal) 

for their outstanding work in connection with the Coral Sea and Midway actions. 

COMSWOWESPAC letter 00204, August 10, 1942, and COMSOWESPAC message 

2207512 August 1942. Franklin DeIano Roosevelt Map Room. The recognition was not 

forthcoming! 

6. Nimitz Command Summary, 1942, Volumes I and 11. This record clearly reflects the 

influence of COMMT on the command decisions made by Admiral Nimitz. History 

Collection IVW11.2.2. 

7. CINCPAC OPPlan 23-42, 29 April 1942. This pIan controls the activities of TF16 

IHalsey) and ib relationship to TFs 17 (Fletcher) and 12. 

8. "Control of Dissemination and Use of Radio Intelligence by the U.S. Navy in 1942." 

This file in the histmy collection contains a 1942 memorandum from COMJNCH directing 

that messages containing COMINT must be burned after reading. IVQ.5.1 

9. "Potential Value of Radio Intelligence in Naval Battles as Illustrated in the Battle of 

Midway." A report prepared for commander Joseph N. Wenger, D/Chief OP-20-G, on Nov 

9.1942, by Ensign John V. Connorton. 

10. "U.S. Navy COwm Organization and Manpower, 7 December 1941-May 1942." 

History Collection IVWI.3.20 
11. "Organization of UP-20-G, 19361950." For the period February-June 1942,'this Gle 

contains the structure and names of persons in charge following the February 1942 

reorganization of OP-20-G. History Collection IVWI.4.1. 

12. Frank Jack Fletcher, Admiral USN, Battle Report after Coral Sea, 28 May 1942. 

History Coll~on IVWW.8.1 

13. "Communications Procedures and Daily CoMIm Summaries from Hypo." This file 

contains messages dated March 1942 between Washington and ~onolulu. History 

Collection IVWiI.3.4. 

14. "Cryptanalytical and Decryption Operations." A 1941 memorandum on this subject 

from OP-20-G to VCNO criticized the odd-even arrangement between Army and Navy, 

mentioned the peacetime rivalry, and the Army's light workload in contrast with the 

Navy's expanding efforts against a variety of targets. The Navy's right to distribute 

intelligence to the White House is also mentioned. History Collection IVU. 1 

15. Intercept Station C Fmm Olongapo through the evacuation of Corregidor, 1929-1942, 

This booklet was published by the Naval CryIptologie Veterans Association. It contains 

articles written by oEcers and men who served at Station C during the above perid. 

16. Forest R. Biard, Captain USN(ret1. A personal account of his experiences as the 

linguist in a radio intelligence detachment aboard the Yorktown during the Battle of the 

Coral Sea Written after the event, this narrative wntains the only known minub-byminute account of the battle from the point of view of the linguist and the intercept 

operators. 

Oral Histories 

a Thomas H. Dyer interviews 1-6 by Paul Stilwell, Oral Historian, U.S. Naval 

Institute, Annapolis Maryland, between August and September 1983. Dyer was 

semd in command under Roc hefort during the period covered by this chapter. (U) 

b. Stuart McClintock, cryptanalyst in OP-20-G, who worked exclusively on JN-25 

messages beginning two weeks after Pearl Harbor. NSA OH #03-81. (TSCW) 

c. Joseph 6. Rochefort, OIC of the Hawaii RI center during the perid covered by this 

chapter. In this interview, conducted by the U. S. Naval Institute, a partial 

chronology of his career can be reconstructed. History Collection IVWX.l (U1 

d. Durwwd K. (Texas) Ftory, Chief Master at Arms, 14th Naval District. Afeer the 

Japanese attack on Pearl Harbor, when manpower requirements at Hypo 

increased exponentially, Rory was delegated to personally recruit new workers for 

Hypo from the replacements who arrived in Hawaii almost daily. His success rate 

became legendary after he selected and assigned band members from the 

battleship California. NSA Oral History OH 27-84 (SCCO) 
e. Wesley A. (Ham) Wright, Captain USN (ret). NSA Oral History, OHll-82. 

(FOUO) 

f. Rudolph T. Fabian, Captain, USN (ret). NSA Oral History, OH09-83. (S-CCOI 

Secondary Sources 

Brown, Anthony Cave. "C": The Secret Life Of Sir Stewart Menzies, Smmrrster to Winston 

ChwchilL New York: McMiHan Publishing Co., 1987. 

Buell, Thomas B. Muster of Sea Power: A Biography of Fleet Admiral Ernest %T. King. 

Boston: Little, Brown and Company, 1980. 

Costello, John. The Pacific War. 2nd printing. FairfTeId, Pa.: Faifield Graphics, 

February, 1982. 

Domart, Jeffrey M. Conflict of Duty: Tk U.S. Navy's I&Iligence Dilemma 1919-1945. 

Annapolis, Maryland: Naval Institute Prew, 1983. 

Holmes, W .J. Double-e&ed Secrets. Annapolis, Maryland: Naval Institute Press, 1979. 

Horner, DM. Special Intelligence in the Southwest Pacific Area in World War II. 

Australian Outlook, Jod of the Am. December 1978, Vol. 32, #3. 

Hoyt, Edwin Palmer. Blue Skies and Blood: The Battle of the Coral Sea. New York: Paul 

S. Erikson, Inc., 1975. 

Kelley, Lt. Welbourne, USNR, and Calter Karig, Commander USNR. Battle Report: Pearl 

Harbor to Coral Sea. Farm and Rinehart, 1944. 

King, Ernest J., Fleet Admiral, USN, with Walter Muir Whitehall, Cdr. USNR. Fleet 

Admiral King: A Numi Record. New York: W. W. Norton and Co. Inc., 1952. 

Layton, RAdm Edwin T., USN (ret), with Captain Roger Pineau, USN (Ret) and John 

Costello. And I Was There. New York: William Morrow and Co. Inc., 1985. 

Lundstrom, John B. A Failure of Rdw Intelligence: An Episode in the Battle of the Cord 

Sea. CryptologiQ:, Vol. 7, #2, April 1983. 

The First South Pacific Canapaign: Pmific Fleet Stratem, Decern ber 1941-J~~~ 

1942. Annapolis, Maryland: Naval Institute Press, 1976. 

Millot, Bernard A. The Battle of the Coral Sea. Annapolis, Maryland.: Naval Institute 

Press, f 974. 

Morison, Samuel Eliot. History of U.S. Naval Operutions in World War 11, Vol. IV, "Coral 

Sea, Midway and Submarine Actions May-August 1942." Boston: Little, Brown and 

Company, 1971, 

Morton, Louis. U.S. Army in World War II, Strategy and Command: The Firsf Two Years. 

Washington, D.C.: of the Chief ofMilitary History, Department of the Army, 1962. 
Potter, E.B. Nirnitz. Annapolis, Maryland.: Naval Institute Press, 1976. 

Thorne, Christopher. Atlies of a Kind: The United SWs, Bribin and the War Against 

Jupn, 1941-1945. New York: Oxford University Press, 1978. 

Willmott, H.P. The Barrier and the Jauelin: Jupumse and Allied Pacific Strategies, 

February to June 1942. Annapolis, Mary land.: Naval Institute Press, 1983. 

Window, Captain W.G. USN mt). Th Fleet the Gods Forgot: The U.S. Asiatic Fleet in 

World War fl Annapolis, Maryland: Naval Institute Press, 1982. 

Japanese Sources 

Hattori, Tdushiro. The Complete Hisbry of the Greater East Asia War. Four volumes. 

Masu Publishing Company, 1953. 

Saburo, Ienaga. The Pacific War, World War II and the Japanese 1931-1 935. New York 

Pantheon Books, 1978. English translation by hndom House, Inc., 1978 

Shiumada, Koichi. Air Operations in the Philippine Islands. 2nd edition. Annapolis, 

Maryland: U.S. Naval Institute Press, 1971. 

The Japanese Navy in World Wur IT: An Anthology of Articles written by former Japanese 

Nud and Air Defense Officers, 2nd printing. Initially published in Prweedings between 

1952 and 1958. Annapolis, Maryland: U.S. Naval Institute, 1971. 

Part Two 

Primary Sources 

1. Record Group 457, National Archives 

a. SRHOl2 RIP98. The Role of RI in the AmericadJapanese War, Vol.11. 

b. SRH230, Battle of Midway, Henry F. Schorreck. 

c. SRH268, Two memorandums dated June 1942 to ACNO (Assistant Chief of Naval 

Operations) from DNC (Director Naval Communications, Joseph R. Redman) md 

OF-20-G (John R. Redman) subject: Radio Intelligence Organization and 

Establishment of Advanced Intelligence Centers. 

d. SRH272, CIWCPAC Enemy Activities File. 

e. SRH278 War Diary, CIU PacZc 1942.IHawaiil. 

f. SRMN004, CINCPAC Intelligence BulIetins, 16 March-1 June 1942. 
g. SRMNOOS, OF-20-G file of memoranda and reports relating to the Battle of 

Midway, 1942-1946, 

h. SRMN008, CINCPAC and Corn 14 CI BulletinsIRadio Digests, 1March31Decemhr 1942. 

SRMNOIB, Corn 14 TI Summaries with Fleet Intelligence Summaries. 

j. SRMNOIS, The Establishment of Advanced Intelligence Centers, May 1942- 

August 1943. 

k. SRNS1517, Daily TI and CI Summaries from Melbourne, 20March4une 1942. 

2. Record Group 38, National Archives 

a. CINCPAC message file. This file contains all classified messages sent and 

received by CINCPAC during the period covered by this chapter. 

b. Sources of Intelligence: A memorandum from Chief of Staff, Naval Forces 

SOWESPACFOR area indicated that by 26 June 1942, air reconnaissance and 

photography were the major sources of information on enemy bases, dispositions, 

air stre@ and air losses. The memorandum also indicates that reconnaissance 

flights were flown to confIrrn intelligence reports from a third unspecified source 

other than radio Tokyo. 

c. A memorandum from the Commandant of the Marine Corps (CMC) dated 28 

August 1942, addressed to "Suhhief of Naval Operations" and meaning ON1 or 

OP- 16-X; subject: "Establishment of Joint Intelligence Centers." This 

memorandum conveyd two earlier letters from CMC to COMINCH dated 24 

March and 10 April 1942, same subject. (Sec Nav/CNO Correspondence) 

d. 24 March 1942 memorandum from [General] T. Holcornb, CMC to COMINCH, 

subject: Establishment of Advanced Joint Intelligence Centers. 

e. 13 April 1942 memorandum from COMINCH to CINCPAC Fleet, subject: 

Establishment of Joint Intelligence Centers. 

f. 28 May 1942 memorandum from CINCPAC Fleet to COMINCH, subject: 

Establishment of Advanced Intelligence Centers. This memorandum from 

Admiral Nimitz to Admiral King nonconcurs in the scope of the CMC proposals. 

Nimitz advocated an intelligence center only in Hawaii centered on the Corn 

14Hypo organization. This center was to be established fust and possibly followed 

by others. 

g. Records of CNOICOMINCH: Under the file heading "Air Combat Intelligence 

Officers" will also be found the basic CMCjCOMINCH correspondence of MarchApril 1942. Reviewed by &%dm J.B.Towers, Chief of the Bureau of Aeronautics, it 

generated a separate plan for providing air combat intelligence officers in the 
prom Joint Intelligence Centers. Towers also tad4 BuAir C kain the 

who would be selected to serve in the centers. (1 May, 14 May, 21 May 19421, 

h. 14 July 1942 memomndum from COMINCH to VCNWONI) subject: Air Combat 

Intelligence mcers. This memorandum agreed with CINCPAC's wish to have 

the center in Hawaii completely operational beEore other centers were opened in 

the P+. An aecompaaJring 1- from CIPJCPAC to COMINCH skhd that tha 

Ha* Center CICPOA) was up and mmkg under Corn 14. 

i. On 31 March 1942, COMINCWCNO approved establishment of an Aviation 

Intelligence Branch in the BuAir to develop and " hTtxhnid Aviation 

Intelligenceu ashore and afloat The normal sources of this infomation were OM 

ad photography. 

j. 10 April 1942, Admiral R. K. Turner, Chief of War Plans for Admiral King, 

proposed that OM meate an Intelligence SM for Admiral Gbormtey, newly 

appoinfed~~,So~~Area,wb~raweretobeh~ 

at Auckland, New Zealand, with an advd base at Tongatabu. 

k. In May 1942, Commander Pitzgerald Greene, ONI, was sent to New Zedand to 

operate a center staffed by 300, including an RI element! 

1. A memodum dahd 5 June 1942, from MGen George V. Strong, A-2, to 

COS George C. Marshall, U.S. Army, w& Cooperation and Collabmtion with 

the Navy on Military Inklligence. Two covering notes from Admiral Russell 

Wibm, OM, probably ta Admid Emst JJ. King, COMINCH, nob a negative 

Navy reaction aRer seeing the Army memdum. Remrds of COMINCH Box 

ma. 

3. Nimitz Cod Summary 1941-1942. An oE&l CINCPAC rd of& ideas, 

plans and concerning events in the Pacific. A daily xeaord of important 

from 22 February to 8 June 1942. History CoIlection, TVWII.2.2 

4. Histoty of OP-X@GY-P-1 (Cryptanal+P&). This Mud hist~ry is in the 

histmy eolleetian IV WL6.12 and -5.1 3. 

5. History of OP-2[FGT-P fhE~~e AnalysbPacXc). This &s&ed history is in the 

history collectian. IV W 1.5.8. 

6. CNO Summaries of Japanese Naval Activities (Midway) 14 AH130 June 1942. Thes 

daily intelligence summaries were prepared by ONI and loeated in ths mrds afthe White 

House Map Room. 

7. CINCPAC Intelligence Bulletins (Midway) 16 March-1 June 1942, Daily. This ia OP2MXs copy dthe Bulletin. Cryptulogic Archives Holding Area, ACC#17907A, fAlcation 

CBKH44. 
OPd Histories 

a Interview of Joseph Rochefort by the Naval Institute. Hishy Collection, IVWX-1. 

b W. A. (Ham) Wright, NSA Oral History, 11-82. 

c. Thomas H. Dyer. Interviewed by Paul StilweI1, Oral Historian, U.S. Naval 

Institute. 

d. Adm. Edwh Layton. Interviewed by Mr. Robert Farley, Oral Historian, National 

Security Agency. NSA OH02-83 and follow-up, 32-83. 

Secondary Sources 

The Butte of Midwuy Iwlrsding the Aleutian Phe, June 3-June 14,1542, Strategic 

and Tacticd Analysis, U.S. Naval War College, 1948. History Collection IVWVII.6. 

Buell, Thomas B. The Quiet Warrior: A Biography ofAdrniral Raymad A. Spruunce. 

Boston: Little, Bmwn &Co., 1974. 

Colville, John. Fringes of Power: 10 Downing Skeet Diaries 1939-1955. New York: 

W.W. Norton Co,, 1985. 

Costello, John. The Pacific War. 2nd printing. Fairfield, Pennsylvania: Fairfield 

Graphics, 1982. 

Dyer, VAdm George C. USN (Retl. The Amphibians Came to Conquer: The Story of 

Admid Richmond Kelly Twner. Washington, D.C.: U.S. Government Printing Office, 

LC#71-603353. 

Furer, RAdm Julius Augustus, USN (ret). Administration of the Navy Department in 

World War ll. Washington, 1959. 

Hough, Richard. The Greatest Crusade-Roosevelt: Churchill and the Navd Wars. New 

York; William Morrow LCo,, Inc., 1986. 

Hoyt, Mwin P. Japan's War: The Great Pucific Conflict 1853-1952. New York: 

McGraw-Hill Book Company, 1986. 

Keegan, John. Tk Face of Battie. New York: The Viking Press, 1976. 

The Musk of Comd. New York: Viking Penguin Inc., 1987. 

The Price of Admiralty: The Evolution of Naval Warfare. New York: 

Viking Penguin Inc., 1988. 

Larrabee, Eric. Commander in Chief: Franklin Delano Roosevelt, Xis Lkutenulbts, d 

Their War. New York: Harper and Row Publishers, 1987. 
Layton, RAdm Edwin T. USN et), with Captain Roger Pineau Ub..d (retl and John 

Costello. And I Was There: Pew1 Harbor and Midway - Breaking the Secrets, New York: 

William Morrow and Co., hc., 1985. 

Lord, Walter. Incredible Victory. New York: Harper and Row Publishers, 1967. 

Lundstrom, John B. The First South Pacific Campaign: PaciJic Fleet Strategy 

December 1941 June 1942. Annapolis, Maryland: Naval Institute Press, 1976. 

Marison, Samuel Eliot. Hisbry of U.S. Naual Operalions in World War lI, Vol. 111, 

"The Rising Sun in the Pa&x," and Vol. IV, "Coral Sea, Midway and Submarine Actions 

May 1942-August 1942." Boston: Little, Brown and Co., 1971. 

Potter, E.B. Nimitz. Annapolis, Maryland: ~aval Institute Press, 1976. 

Range, Gordon W., with Donald M. Goldstein and Kathleen V. Dillon. Mimcle at 

Midway. New York: McGraw-Hill Book Co., 1982. 

Taylor, Theodore. Mitschr the Magnificent. New York: W.W. Norton & Co., Znc., 

1954. 

Tuleja, Thaddeus V. Clim at Midway. New York: W.W. Noxbn & Co., IN., 1960. 

Schaller, Michael. Dough MacArthur: The Far Emtern Gem&. Oxford University 

Press, 1989. 

Willmott, H.P. The Burrier and the Javelin: Japnese ad Allied Pacific Strategies 

FebruuryTTune 1942. Annapolis, Maryland: Naval institute Press, 1983. 

Japanese Sources 

Fuchida, Matsuo, and Okumiya Masatake. Midway: The Battle That Doomed Japan. 

Annapolis, Maryland: U.S. Naval Institute, 1955. 

Hattori, Takushiro. The Cornpkte History of the Greater Eut Asia War. Masu 

Publishing Co., 1953. 

"The Japanese Story of the Battle of Midway," ONI Review, May 1947. (A translation 

of Admiral Nagumo's action report.)