· .. 

. . . 

. . REF ID:A6565~ . 

emorandum . • UNITED STA~BS GOVERNMENT 

TO ~WENGER (V'lce Director, BSA) 

PB.OM I CAPr ROEIER ( Op-322!) 

SUBJECT: Ol!lG Report :/168; forWard1Dg of 

Encl: (1) Dir., OEG Report ser (L0)2271-52, undated 

(2) OEG Report :/168 

Op-32.'i!r/rdw 

DATB: SSO/Y-137 

J APR 1953 

l. Enclosures (1) and (2) are forwarded herewith for 1nformt1on and retention. 

/2;.. 7. 

B. F. RCEDER 

Page l of 1 Page 

Copy L of 2 copies 

roved or release b NS on 08-23-2013 ursuantt E .0. 1352 
Fro.Ill: 

To; 

Via: 

subj: 

Encl: 

Director, Operations Evaluation Group 

Op-03D 

Op-)22Y 

(I.,0)2271 .. .52 

Forwarding of Enclosure (1), Ogerat1ons Evaluation 

Group Regort 68, TOP She:R!lf ef.dfelo 

(l) OEG Report. 68: 1val~at1on ot the Role ot Decr,ption Intelligence in tAe Operat1ol181 Phase of the Battle 

ot the Atlant1oo 

lo The attached report, prepared at the request of op-03D and Op=)~2Y 0 should be viewed as an eX&Dlple of the kind ot intorinlltion whioh can be obtained by an extensive study of the data 

extracted from the decryptions by both tb.e Germans and tne Al• 

lies Of .radio COaQlUWliO&tions pertaining tO t.b.e Operations Of 

tbe German sub.marines aea1nst Allied shippi.ug. This study has 

established e nwu.ner of conclusions ot wide general interest to 

all those concerned with the Radio war, and w1t4 the con4Qct ot 

anti-submarine 09erati0Aa, 

~o No effort is·made here to recapitulate tlle findings ot this 

study on the use of decryption intelligence to our own torces 

and to convoy sa1'ety, since t.tleae s..ibJeots are covered in tb.e 

swnmar1 of the repor~, part 5. fheae t1'1..4inss warraAt ca~Qf..Ml 

reconsideration~t the oonoJ.usLaAs reached lnCilliiFS~~n 

w~iie_!ft~itil or--acoryptioA 1ntelilgelioe "'Were not ts!Cen into acooLWt. - - - -------- -- ·-----··------.... 

)o D1stribut1~n of the attached report to all properly cleared 

staff agencies concerned with snt1-submar1ne warfare and submarine opera tion.s is recommendecle 

JAOIN'l'O STI!:INHARM', 

Director, Operations £valuat1on.Groupo 

T 0 P S E C R E T GANOi; 
Tot' 5WlmT L ~F :w~~6AOE~ (Lo)2211-s2 

?'f- t -~:CCI\: ~ 

SECURITY INFORMATION 

OPERATIONS EVALUATION CROUP 

REPORT 68 

!.'VALUATION OF THE ROLE OF 

DWRYPTIOI-1 llfl'ALLIGENCE IN THE OP.ER/\TIONAL PHI.SE OF THE 

BATTLE OF Till; ATLANTIC 

T 0 P S E C R E T CANOE· 
'PeP s:&;s1m' O ~F :W ~~~o E 4t-- r ~:CCI\: -· 

SECURITY INFORMATJQri TA o:r CONTENTS 

BillLJ;OGliAPHY 

PREFACE 

INTRODUO'J:IION 

lo HISTORICAL SURVl!.Y 

-

(L0)22?l=S2 

2o THE EX'DNT OP DECR!!>TED IMELLIGENOE AVAILABLEo 

2olo To the Germans 

2o2o To tlle Allies 

)o 'l'.HE UTILIZA.TlON OF DECRYPTION INTl!iLLIGENOE BY THE GERMANS. 

)olo The Etteot ot x-B Intelligence on the Oapabilit1 of 

UaBoats Contacting a Oonvcyo )ololo Effect ot X-B Intelligence on Probability at 

Co.ntaoto 

3olo2o fhe Contact ooett1cient and Operational sweeprate~ 

3o2o The Effect ot X-B Intelligence on the Attack Factor .· . and the Sinking Rate o 

4o TBX VALUE OF DEORY.i.>TION INTJ!:IJ,IG'}l::NOE TO THE ALLlES. 

4olo Strategic Use 

4o2o Tactical Use in the Defense ot Oonvo7s. 

4o3o Offensive Use 

4o)olo HUAter-Xiller Operations against the U•Boatso 

4o)o2o Allied Decryption Intelligence in Relation to 

the Destruction ot the German Refuelling Fleeto 

5 o SUMMARY AND CONCLUSIONS. 

ANNEX to .Part 21 Section 2olo 

GKRt;A.N X-B INTELLIGENCE OF NOl:lTH A~LANTIC CONVOYS. 

ANNEX to part 21 section 2o2o 

DA.Y BY DAY SUMMARY OF ALLIED DEOHYPTIONS OF GERMAN 

U-BOAT MhSSAGES. 

ANNEX to part 3 o 

OP~TIONAL DA!rA. 

ANNEX to Part 4, section 4o)a 

JECRfPTIONS OH INDIVIDUAL U-BOA'l1S. 

T 0 P S E C R E T CANOE 
TOP Sl£mi! • 0 rFcI~: ~~5~L. '6 

u .J.j ~ .J.. '- .&..I Jllll' (L0)22?l-52 

SECURllY lNFORMATllN ! 1 1 Q Q ! ! ! !! x 

Ia SOURCliB 

Al .flermaa 

(a) X-B Beriolltea Weekly rep\)!'fiS ot the Ger.man decryption service (X-B DJ.enst)o Captured at e.nd or waro Extend 

trom 19)9 through Agril 19440 Complete record ot all 

German Raval 1ntell1geacea The deol'fptions deal al.most 

entlrel.J with convo1 movem.enbso (&eeret) o 

(b) 'l'he war D1aey of Betehlsbaber der_unterseaboote (Bero), 

(COJDmaDder ot Sub.marines)o From 19)9 through December 

19440 (Caat14ea•ial)a 

Pl ~lie~ 

(o) Files by elate of Decrypted Messages .read by 

Op-20-)-GI(A)o (Top aeo~et Ul,ra)o 

(d) Dl1ly U-Boat Bstimateo COM'.INCB daily charts with U-Boat 

&lld convoy positions glottedo (Bocrei)o 

Ile REFERENCES 

(e) Account of U/B war froa December 1942 - May l94;a 

Co.m.p1le4 by Op-20....)··GI(A), dated 29 October 194Sa 

('Pep See»et Vlt=a ) o . 

A ve17 oo.mprehensive, thorough» extre.mel1 interesting aocoUllt ot the task acoo.mplished by the group during World war Ilo It is in five volWDSs, as follows: 

./' Volo I - Al.lied Oo.IWllWlioati~s Intelligance and the 

Battle of t.be Atlantioa A SWD018l.'Jo 

Volo II N U•l30et Operat1onso This is in five parts four dealing with auooessive periods in the Battie 

ot t~e Atlantic! and the fifth with blockade runners 

and German Nava Operations in the Fer East and 

Indian. Oceano The role ot decryption intelligence is descr1be.d throughout eaoh period, chiefly by means 

ot case histories ot particular convoyso There is a 

VeJ!7 comprehensive collection of these oese histories 

oovering the us .. tJK, US-Gibraltar, end UK~-Gib.l'altar 

conv01s at certain periodso 

B-1 

T 0 P S E C R E T .CANOE 
..... ~F ~~f;JO,.,~ 

'?Cf SBCRl'f ~ 0 r ~ n t I\:~~ (L0)227lftS2 

--sE£\}R\~1Jti0nAJJJ9!t CQUW11oation IDtelligance llD4 

Oo.mpro.m1se ot Allied Cip.b.erso _ 

This volwae oon,ains a Vert interesting aocow:at ot 

the manner in w.b.10.b. Op-20-3-GI"(A) prove4 tllat the 

Allied messages were being rea4 by the Germans~ 

Vol. IV - Teo.bnioal Intelligence from All1e4 Co lcr I 

neecribea the contribution of Allied 4eo17ptlon 1ntelllgenoe oonoerni~S Ger.man UoBoat material and 

armament a . 

Volo V • TJ:Le German Naval Grid an4 Its Oiphero Ve17 

interesting description of techniques ~sed in 

decoding the German grid cip.b.era 

.( t) G.c. end o •. s. Naval Historyo W;p See•e• Ul,:rao 

This ls a compendious aooount of the work ot the British 

Naval Intelligence Oftioe, 1n 24 volu.caes. A ve~y excellent histor7 or tne u-Boa~ war is presented 1n Volume 

./ XVIII, "The Battle ot the Atla.a.t10o" 

(g) ORG secret Memorandum No .. 18: rrequeacr ot attacks on 

Oo.n.voys in Relation to U•Boat Predioti~ns, 18 November 

l942o 

(h) ORG Seoret Memorandum mo .. 2S: A Probability Study ot 

OOMIHCH .Da117 Submarine Estimates, 27 February l94)o 

(1) 

( 3) 

OEG cont1dent1al Report No. 51: A.o.tis~bmarine wartare 

in world war II, 1946. 

OEG cont1dcnt1al Report NO. ~6: Searob and screening, . 1946 

(k)v G.c. and c.s. Naval 61.gintD Vol. VIIo - The German Navres 

Use ot Special Intelligence aad Reactions to Allied useo 

!le;t1 Deere~ Ul,no · 

Covers the subJeot in narrative form trom 19)8 to tne end 

ot the waro Contains so.me case histories ot speoitio appl1cat1ans ot Ger.man deoryptions of Allied Rlo In ad= 

dition to t.be weekly X•B reports, the author .tlad available 

the captured daily files of German decry~tso 

!OP 6l!SHii9;' B•2 

PRllC-NSS-3U6 TOP SECRET~· 
SECURITY INFORMATION PREFACE 

This report contains the findings of research carried out 

with the general obJective ot determining in what manner and to 

what extent th.a aveileb1lit7 ot intelligence derived trom the deor7pti~n ot intercepted radio messages affected the conduct 

ot the U-Boet wer against North Atlantic convoys on the part of 

both belligerents. The speo1t1c purpose ot the research can be 

most olearl7 steted by giving the oircum.stanoes connected with 

the genesis of the projeoto 

Dllring World War II the Antisubmarine Operati~ns Research 

Group (ASWORG) was organized tor the pl.lrpose primarily ot analyz= ing operati:>nal data as thef were assembled in the course of the 

war against the Germ.en subm.erines, 14 :>rder to provide information 

that would be ot assistance in adapting strategy and tactics so 

es to utilize the available A/S foroes with maximum. etteotivenesso 

In the course ot tb.is work, /.S\"M'OHG found it necessary to devise 

measures of efteotiveness tor the various aspects of the A/S 

operations--as an example in dealing with the detection ot the 

enemy, subjects or study by ASWORG included the construction ot 

systematic searcn plans tor surtaoe vessels and aircraft; the 

evaluetion ot the means ot deteotion--visual, rader, sonar; studies 

ot tne most profitable areas ot search, etc. At the end ot the 

war, the most ialportant results ot tlle various studies carried 

out by ASWORG were assembled and published in two comprehensive 

reports: reference (i) dealing chiefly with the several aspects 

ot the war against t.b.e u-Boats trom a statistical vi.ewpoint; and 

reference (J) presenting a complete end coherent theory ot search 

and screening operations developed on the basis ~t the operational data assembled during the war. 

To be efteotuel ~perations research requires as complete operational data, bolh own end ene.1111's, as possibleo The results 

ot intelligence in general were, ot course, .made available to. 

ASWORG. Certain aspects of intelligence itself pertaining to the 

antisubmarine effort were subjected to analysis by the Group. For example 1 reference (g) contains en investigation of the relationship be~wee11. attacks on c~nvoys and the predicted positions of U-Boats shown in the COMINCH daily submarine esti.illete, thus 

providing a means of estimating the accuracy or U-Boet tracking. Reference (h) is a turther study of the accuracy of the OOMINOH 

daily submarine estimate; in this paper, the displacements of 

evaluated sub.marine contacts tr~m the nearest plotted subawrine ~n the chert last issued before the time of contact served as 

a basis t~r the anal7siso 

P..1 

TOP S E C R E T .. CANOE 
(L0)2271=52 f6F 9BSRET ~ litID rf~\6!5ft°E ,, SECURlJi}' J~.rgeac. derlved by maans or tile aaoryption or 

Ger.man. radio oommwi1oat1on.s, however was tor seourit7 reas:ms n~t speoitioally identified as s~ch !n the 4ata made available 

to ASWORG. The quest10ll eventually arose whether the inability 

on the part or ~ operations analysts to t&ke into aocowit 

the taotor ot special 1ntell1genoe had resulted 1n in.accuracies 

in the dete.l'ID1.nat1:>a ot aertein parameters still ot current 

1mgortanae in opentit>ns research. AS ex.amples ot such peralllB ters can be o1'84 the theoretical sweeprate ot sub11LBr1.nea. 

which had been 4eter.aiined from ~perational 4ata provided bJ 

ow.- ~a aubaar1nea operating in tu.e Paoit1o (reference (1) ); force require.meats tor sighting submarines bt aircraft (reterenoe (~), p. 98) were computed without being able to d1at1Agu1sh between. oases 1n which deor1ption intelligence located 

the target eubaarlne aoouratel1, a.ncl those oases where the 

aearoners were restricted to uaia.g the results ot probab111t7 oans1derat1ons onl.7. It has been pos~ible, in the course ot 

the present in.vea~1gat1on., to determine the operational sweeprate ot the German U-Boats, when the7 operated witbout the aid 

ot operationally 41Set&ll 4eor;ypt1on intelligence, ana the ettect 

suoll 1ntell1genca .bad on their performance~ Moreover, data 

which make p~asible a oomparis~n ot sweeprates ot aircraft carriers 0J1 submarine targets, as these are affected by decryption intelligence ere presentedo 

It should be stressed that tb.ia report is in. no sense a 

COlllprehenaive evaluat1:>11 of tbe part pla7ed by decryption 1ntel~ 

ligenoe in the war against tJle U-Boats. It is concerned only with the partic~lar etteot which deorypti~n intelligence had on 

the oapab111tJ ot the U-Boats to con.tact and attack convoys. and 

on the oepab111tt ot the allies to counter tll.ese operations of 

the U-Boata defensively and ottensivelJ. Other aspects ot de= 

oryption intelligen.oe. auoh as its technical applioati~ns to 

new weepon.s1 searo.b equipment, countermeasures to these, etc., 

are not 4ea t witll. 

Attentioa is oo.ntined to the convoys that traversed the 

North Atlant1o between the United States - Canada end the United 

K1ng40ta .. the eastbotlncl BX and so, and the westboWld ON(S) con ... v07s. The period considered is trom Jul7 1942 to Maroh 19440 

From the viewpoint of this atud7 1 this :>verall intervel can 

oonve.nientl1 be <:ivided into t:>ur perio4·s: Period I. Fro.m l July 1942 to )l December 1942. During this 

time the Germans were reading the Allied oonv:>J trettio 

with some suooese. ~e Allies were not reading the Ger.man 

tratt1o. (Part 2) 

P..2 

TOP SECRET .'1CANOE 
TOP SE ERE T ~ANOE-
(L0)227l=.52 

The U-Boat-oonvor war had oertain pec"111ar aspects which 

poaed speoial problems tor Intell1genoe. On the part of the 

GerJll8lls, there was the tact that uless they oould preve.ut the 

·Allies troa shipping enough .ma ter1al they o_,uld not p.reven t an 

1nvas10ll whioll would divide end strain their lend t~.roes be7ona 

tale breaking point. To aoooaglisb. tb.is mssi:>n1 they had available enougb 8Qb.marines to be able to keeg troa at least 40-60 

at sea at all tiales after Pearl Harb~r a.ad over 100 tor the 9 

uatlls tra ootober 1942 to JWJ.e 1943· 'lhe great sr.a~t>rity ot 

these, ll.oweve:r, were tile BIBll 500-T t1pe VII O. TheJ had a 

l:>ng 1ir&As1t troa even tb.e J'renoh ports to the aost promising operating areas• as a :result the a"lerage t1.M spent on patrol 

was onl.7 t.rom 16 to 20 da7a, unless theJ could be refuelled at 

tlle1r statl~s, 1.n whioh oaae theJ 001214 reaJBiA for as muoh as 

32 - 36 4a7s. Good 1ntell1genoe oa convo1 .movem.emts would aid 

1a ettecting eoonomy ln their uae, in that 1t would .make it 

possible to veotor the boats QA to targets lal.JWn to be in a 

certain l~oal1tf ~~1nstead ot requiring them. to devote much ot 

their possible errort to reoo1111a1ssance. Moreover tlle Ger.man 

Submarine Command was oonvinoed that iJl\)1"8 s1llk1ngs would result if a promising oontect were exploited bJ a large number 

ot attacking U-Boats, rather t.ban distributing the boats among several p~seible simultaneous o~ntaots; hence from their 

viewpoint g~d 1ntell1genoe was requi~ to aid in disposing the boats in such a way as to attain this end. Si.nee aircraft reo~n.neissanoe was available to the Ger.mans ~nly to a very 118'11ted extent, and .herdl7 at all with regArd to l1IC-UB convQys 1 the deorypti~n ~t Allied radio oomm..m.ioati~ns, oonteining intorm.ation ~n sailing ro~tes, ren4ezvo~s with escorts, and 

so&U8t1JJ&s ourrent positions, wes their best s~uroe ot 1ntelligenoe on c~nvo1 shipping. With the exoepti;)D ot •everal 

periods ot oo.1119e~otively short du.retion, the Germans read the 

convoy oode partially but fairly consistently for nearly lA 

years after the entry ot t.be United States into the wero 

Fro.m June 1943 on, however, thef were able to read practically n~thing except some messages which gave stragglers' routes 

and eer!J rendezv~us points, and the sgb111Ar1ne command suspected .ma117 or these t~ be deoegtive. Eve.n tbis soanty source 

dr1e4 ~P in December 1943, when the Allies began to avoid giving definite looatioas, using reference points instead. This situation did not improve, up to the end of the war. (The extent 

&Jld use by the oer.mans ot epeclal intelligence is discussed in 

parts 2 aa4 3 ot this report.) 

l-1 

TOP S E C R E T \CANOE 
(L0)2211 ... 52 

e on rt llandle4 their 1ntell1sence problem in the u~Boat war by evaluating all the 1ntor.met1on ot u-Boat 

movements that came in trom every possible source in order to 

plot the probable locw~iona ot as .many U-Boats as possible, thus 

prov141n.g e g&l14e t~r tile evasive routing or diver~1ng of con~ 

VOJB and tor the vectoring ot task groups or other toroes tor 

the speo1t1o m1ea1on ot hunting dowa tbe aubaarines. A. verr 

importan.t aoLU'Ce ot intelligence was provided by the aeevy ra41~ tratt1o oarr1e4 ~a by the Germans, .n.eoessitated b7 the 

firm 0011trol that the submarine OOJUlllnd kept on the boats 111 

order to ca1'17 out hie sroup ~pa.rations etfectivelyo TJie Ger-

.man rad1o 00DRW11oati:>11a weZ'8 exploited by the Allies 111 three 

wars: 

( l) B7 D1reo t1011 P1n41ng ( D/JI). a method ot looa ting a trans.... - J111tt81' br obta1a1Jlg aiawlteneous bearings oa a transm1s0 

sioa at aeYeral etat1:ms by means ot directional antennae, ' 

and noting the area ot interaeat1on ot the bearing lines. 

This !lletlao4 was ueea ve'J!'I exte11sively and etfeotivelyo 

(2) BJ 14entlf)JJlg the trauJD1tter b7 means ot the Oharaote.r ... ieties of the intercepted transmissi~n. 'l'Wo teollniques tor thle purpose we.re used: 

(a) TINA. a metho4 ot 1dut1~1.llg a radio *-er~tor bJ 

his sen.41ng oharaoteristios. It oons~ed ~f making a tape recording ot each tranSJILission and 

taklAg math9.818t1oal .meaearements ot eaoh dot, aasb, 

all4 8j>808o 

(b) Ra41o J'in.sez Printing (RFP)l a aethod of identifying the red1~ transmitting stat ODo This oonsiated of 

taking high speed pllotographs ot the eleotrioal 

cbaraoteristios ot a transadsslon, which .made pos- sible an. analJsis ot the trans.mit,.;er•s power aupply::i · 

()) BJ obtaining the content ot a radioed oommu.n1oat1on by 

4eor,pt1ng it. 

Deor,ypted messages ware ~t greet strategic value, in Siving t.Jie ope.ret111g areas of the U-Boats even wnen sightings or attacks 

had not ocourrea, supplement!Jlg and checking D/F tixes 1_oal1-

brat1ng the aoc&U"ao1 ot the D/F network, estoblis.b.1ng ~ 

strength of t.b.e packs, a.a.4 providing intor.mati~n oa equip.m.ent and ar.masnent an4 basic taotios. In some oases the intormetion 

in the Jllessages oould also be· used tactically -· either to 

divert a conv~1. or to vector a hunter-killer group 011to a con~ 

centrat1on of U-Boatso 

'l9P S~ORBW ···• 

1-2 

T 0 P S E C R E T . \EANOE 
S£CuRiirmFor1Affcfr g~~1e~ ., (L0)227l-;2 

This report deals partioularl1 with the .P&rt played in the 

operational aapeots ot the Battle of the Atlantic by decryption intelligenoe (3), as 41stinct from. (1) an4 (2) 1 or intelligence obtained in other wayao 

HOU: 

'lDP SBEHlZT 

:o NC -NS S-)• 6 

Thr~Q&h:>u.t the report the oo.mmander ot the Ger- - submarines (Bet8hlabeber 4er u.nterseeboote) la 1'8ferred to bJ the initials ot his German title 

- BclU. 

T 0 P S E C R E T lCANOE 
(L0)227l=52 

BISTOHICAL SURVE! 

From 1940 on the Ger.mans had used some of their com.para= tively few U-Boats to attaok UK-US convoys, but 1.m&nediately after Pearl Barbor dee.mphasized this phase ill order to exploit the opportunities offered by unescorted, independent u. s. 

coastal shipping, with practically no air defense and negligible surface combat ships to make it he:G&rdous. The results during the first a;:mt.bs- ~f 1942 were disastrous for the Allies. BJ 

late spring, however, the campaign began to lose its etfeot1ve~ 

ness, and BdU renewed the attacks against the North Atlantic 

convoys. He was lland1oapped in this cem.paign by the lack of 

sufticient U-Boats until toward the end of the year; but by December he-wes able to operate, on the average, 35 U-Boats in 

the area traversed by the convo7s, and tl1e ni.UD.ber r:Jse to 70 by 

.March 1943. The num.ber ot convoyed sllips sunk became tormidableo 

The landing ot the Allies Lu Africa in November 1942 diverted 

BdU9 s attention somewhat trom th.a Horth Atlantic, and trom 

December 1942 on he pl~oed u-noat grolps or ta1rly large size=-

up to 15 boats--west of Gibraltar to intercept convoys between 

that pQ14t and the United states and caribbeono 

In the North Atlantic, BdU m.ainta1ned a fairly c~nstant 

strategic pattern. BJ the end ot 1941 he knew the general 

rhJ'thm :>f the eastbound BX an4 SC and the westbQu.nd ON convoys he also knew the general routes they tollowedo In acquiring this kno~ledge he ~aa been aided greatly by the dearyptions ot 

radio comrnun.1oet1ons from Allied shore stet1Qns. Hence, lacking specific intelligenoe on a given conv~y, he was able to make a 

tair estimate ot its probable position on a given date; eesilY· 

within 500-600 miles in a generallJ n.:>rth-and-soutb. directi~n, 

and within one day8 s r..m--say 150-200 miles--along the great circle. It he llad a paak ot, say, ten boats spaced 15 miles ap~rt-» 

the7 could sweep out the probable area in about 2 days if the 

weather permitted them to proceed at standard cruising speed. Given fair visib111t7, there was a good chance that they would 

sight the convoy. It the area was one where oonv.:>ys from 

opposite directions pessed each other the probability .:>t a con~ 

tact was 1ncreasedo The German Speaial lntelllgence Service (X= B) had computed these areas ot probable greatest oonvoy density, and, in general, through.out the convoy war, BdU had fr.:>m two to 

six U-Boat gr~ups patrolling these areaso They were disposed roughly in three lines1 and the packs were shifted al:Jng these 

lines as intelligence \Or the lack .:>t it) suggested. In the 

east, the boats were deployed in segments ot a line running south from Iceland to the SOO parallel, somewhere near the 25° 

meridian. The packs on this line were intended to intercept ON 

(west•boWJ.d oonvo7s), ohaue tllea 6Crosa tb.e Atlantic to about 

i..1 

TOP S E C R E T . ·loANOf 
(l.0)2271-52 

1 t eas,ern ot e1.roratt patrol), retuel, and 

then !ue up patrol ea a western paoko ID the west, a line 

was establislled 1n a nearly east-west dil'eoti~n from nortb. 

of Newtoundlaad to the Flemish cap. A third line extended fr~m the south-east tip ot Greenlan4 1n a south-easterly 41-

reo ti :>n to the 4~ pa:rallelo The pack on this line oou.14 be 

used against.both east-bound an4 weat-bolllld oonv~1s, as oocBaiOA BUS&eate4. In add1t10A, boats 1.n tr~nsit traversed the regl~ns aot patrolle4 b7 t.be packs,- &.114 1A several oases convoys 

wer.e oontaoted by these tr&!ls1t1Dg submarines. · 

It la possible that more oontaots aigb.t have been obtained 

by aprea41.aa t;Jie U-Boats mo,,re thinl.7 over tl1e ocean and searching a larger area leas 1nte.ns1vel.7, especially when intelligence 

was gla11titul e.D4 aoo!U'&te, since tlle oonvors were distributed 

more-or-leas at nndom over t.tle whole North Atlantic. Bdtr1 however, aiaLed at getting tJle largest possible number of s1n1c1ngs, rather thaA ot OOlltaots, ud was co.avinoed that in attacking c0J1vo1s it was more protitabltr to have a large nwnber.ot U-B~ats 

c011oentrate4 on a single o~nvo1~ neoesserllt allow!D.g others to 

pass wunolested or even widetecGed. than to attack a larger D\llll= 

ber ot oonvo1s with fewer boats eeoh. conaeq~ently, the value 

to him. ot X•B 1.Dtelligence cannot always be Judgec1 by c:mtect 

rates, es9ecially siJloe tae patrol lines were long enough and 

dense enough to provide a high probability of oontacto 

This oem.ga1gn was one of the most successful during the 

war, tlle everae;;e mon thl.J' shipping losses and tlle exohange re te 

ot mer0Juu1t ships sunk per U-Boa t swik reaching nearl;y their 

highest figures. 

By the middle ot 1181 1943, however, the U-Boat war against the nort.h Atlantic c~nvoys had beoo.m.e extremel1 unprofitable, as 

the toll;,wiLg table sh.::ms: 

Nwnber ot Nwnber ot Eichanse Rate 

Ships Sunk U/B's Sunk: v/V Sunk 

I Bl. U/.B' s ier U/B SWllco 

:rebruar;y 43 )6 10 )06 

Maroh 48 6 800 

A.pril 20 10 2o0 

1187 19 34 o.;6 

ot the 60 tJ-Boats aunk, about halt (27) were sunk by sur ... taoe orattt and halt (30) b7 land-based air; carrier A/C 

aooounted or threeo · 

1-e 

TOP S E C R E T CANOE 
The u-Boats stationed in the M1d-Atlantio did avoid land= 

based A/C, since bases in the Azores were not available to the 

Al.lies unt1l August. However, they ran into the CVE groups-- BOGUE, CARD, CORE, SANTEE. OROATAN--who. during the summer or 

1943, .made a total ot 44 attacks on Ger.man sub~r14es, Sinking 150 and damaging nine, in the area bounded by 25 N to 45 N and 

20 W to 50°wo 

Aside from the losses intlictad on the U-Boats in the M1dAtlant101 the Allied antisubmarine forces gave the Ger.man sub~ 

marine fleet a severe drubbing wherever they encountered them. 

During these three months, tb.e Biscay offensive accounted for )l 

U=Boats sunk; ten more were sunk in th'-Atlantio s~uth of the 

area considered here and nine north of the area; six were lost 

in the Caribbean area and nine in the Mediterranean and the 

Indian Ooean. To offset the l~ss at these SO U-Boats, only 86 

s.hips were sunk by submarines all over the worldo 

It was doubtless the failure ~f the summer campaign which 

convinced BdU that the only region whore a profitable exohange 

rate could be looked for was the North A.tlant1oo Re confidently exP,eoted to meet effectively tlle threat ot the surface escorts, 

wliich had taken euoh a heavy toll of u .... Boa ta in May 0 by means of 

a new acoustic torpedo: tlle threat of A/S airoratt was to be 

countered by improved search receivers and a new quadrupJ.e.,,.mount 20MM A/A gun. Thus, the lest half of September saw the U~Boats 

heading again in considerable numbers for the lanes of the u~-us 

convoys; by Oot~ber their numbers in the North Atlantic were 

comparable with those ~f the spring. This new anti-convoy campaign resulted in dismal tailurs; the exchange rate in October 

in tilis area was one M V sunk er seven U Boats sunk and in 

November the U-Boa s sa no sh pa a a n the Nor h Atlantic, 

although over 30 U-Boets were concentrated there. This stAte 

of affairs continued throughout the winter. U-Boat effectiveness, 

as measured b1 the number ot ships sunk from North Atlantic con= 

voys per U-Boat-day per convoy-day was reduced to one-sixth the 

figure fo~ the period trom July 1942 to May 19430 """ln Maren, 1944, 

the last wolf-pack to operate in the North Atlantic was disbanded. 

The world-wide situation was very little bettero The exchange 

rate for the period from July 1943 to the end of the war was Oo5 

TOP S E C R E T .CANOE 
c10>2211 ... s2 SECURITY INFORMATION . M/V sunk per U-Boat sunk, which was ~ne-eighth the exchange rate 

during the nine-months period tro.m octooer 1942 to June 1943, and ~nl.J one-thirty-sixth the rate tor the nine mQnths preceding 

tbato 

The invasi~n ot Normandy in June 1944 oause4 BdU to oo!P 

aentrat& his b;>ats in the ohannelo By this tiJD.e it meant 

practical certainty ot kill for a U-Boat to aartaoe anywhere 

near tb.eir enemy; henoe the only boats operating were those 

equip.Ped wi tb schnorchel. From this tiale on to the end of the 

war, the GerJDSn submarine ettort was directed egainst coastal 

shipping near the u.x. It was not s~ooesstul, as the low exchange rate indicateso 

TOP 
' 0 f!EF s1E1L~~ ,, 'fe~ SEEJRJ!lf (L0)227l~S2 

SEG~RITY INFORMATION 

2. THE :EXTE1'."T OF D1'..CRYPT!.D INTELLIGENCE 

-~NC-NSS-3•6 

- -XVA!LAStE 

2olo 'l'he Extent of DectLpted Inteliigenoe Aval!ab!e to e Germans. 

2.l.lo General Character of the Intel11Sence .. 

The souroe ot information on Ger.man decryption intelligence 

are the "X-B Berio.hten, which were com.piled and issued weekly by 

the Ger.man Radio Intelligence Servioe--"X""B Dienst 11•-and which 

give a complete summary of all naval intelligence from all sources. 

Decrypted messages of Allied origin are m.E1rked as sucho These 

deal almost entirely with Atlantic convoys. There are practi- / 

cally no decryptions of messages pertaining to combatant vessels; 

exoept tor surface eso9rts (not OVE's) ot convoys9 Tile avail~ - able x~B reports ru.n from the besinni.ng of the war in 1939 through 

April 19440 

The intelligence provided by decryptiono incl~ded, among other less important items, the following information: 

(a) 

( b) 

( c) 

( d) 

Bailing telegrams, giving tb.e route of the convoy in dete:il; 

Diversions ordered after the convoy had left port; 

Rendezvo~s of parts of a oonvo1 from different ports, 

or between the convoy and its escorts; 

Position,. cours·e and speed ::rt the convoy at various 

stages ot the paseage. (The sou.rce or this is not 

indicated very often; occasionally it appears to 

derive from escort rendezvous. As a rulep radio 

silence was observed by oonvo7s.) 

2.ln2o Estimate of the Usefulness of the Deoryptions 0 

The pro.m.ptlless with which decryptions wer3 made available to 

BdU is not indicated in the x~B reports, but the weekly,period 

ot co.m.pileti:>n sets an -outsicle limit. For the purpose ot est1 ... .mating the effeotivenoae of a given piece of useful intelligence, the item is 11 in generai., considered to be "gooarr 11 that 1s 9 to 

contribute potentially to the ability ot the U-Boats to contact 

convoys, it it waa included in the aurrent week's report, or 9 in other words, it it was decrypted with not more than seven 

days' delay. However, this definition is arbitrary, since messages decrypted with more tt..an seven days• delay might still be 

TOP S E C R E T ·~ANOE-_ 2"'-"l 
P••C-NSS-3•6 

TOP S E C R E T l6ANOE 
SECURITY INFORMATION (LO) 2271...,52 

"R•C-NSS-J46 

c-.nd the .BdU war Diary indicate that raaio direction finding ·,-layed Fl very m.1.nor p:srt 1.n furnishing intelligence on Atlantic 

: .. o.nvo,ya., Reconnaissance by aircraft was possible only for 

·nhort perioas bnd at limited ranges from the European coast, 

owing to the unwillingness ot tlle Air Force comaand t~ allocate 

:·.ong. .• rauge pa tr.ol planes t~ the subaiarine cam.peign., 

B7 the ti.me the United States entered the war, the X-B 

service .b.cd au:de l t. possible for tbe Gel'alfill u ... Boa ~ command to 

1:aredic t t.he p.t"Ob6ble areas o:t' grea tes~ dena1 ty ::Jt the OK-US o~nvoyap having obtained enough infor.metion from deoryptions 

to establish the rllytbm o:r sail.iJJ.g und the probable oourses 

they would take. These areas were three in nwnber: 

( 1) 

(11.! 

O.:Li) 

a stripDnorth1ast 8.t NewtoundlandN tl"Om 

45 N-57 N, 44'-'W· .. 49 Nii 

"'ne just a.ortheast ot the to.rm.er, s t1 .. etob.ing 

sc. 11 th trom G1·eenland ~- from 4 9°N .... 59°N; 41°w ... 4) °w ~ 

cr\e stretc_.t.ing a9uth frOlll i'Je~~ee9 Greenland and 

Ioelall4, troa 52°N-63°H 0 2;C\v-2?0w a · 

The value BdU placed on this analysis 1a 1nd1.catec2 by the 

re.ct thct tor nearly two years. in every campaisn against Nort..~ 

~tlantic oonv~ys, he pla~ea his patrol groups chiefly in these 

areas,. lengthening the strips to the southwe.rd when tb.e Allies 

began using a s~uthern route alons the 40°N parallel in January 194:h 

TJ:le o:int-l~·:l.buti.o.n of the x ... a service was stopped in June 

194) by a change i.n tb.e cypher on the part :;,t the Alliesa BJ 

16 September 1943 t.b.e Ger.mans bad suooeedea in breaking a pert of the .new cyp.her; however 11 they were able to read :>nly messages gi v!.o.g st.ragglers' rol'-tea e.nd early rendezvou.s pt>1.ntea This information, t~ j~dge by the BdU War Diary, appears to lla~e been of velue to Oom~Subs in only a few oases; in generalp 1 t may perhaps have been more confusing than belptul.. on l~ December 19.43 the AlJ.iea reaoved tbis last s~u.rce ot 1n..- r~.rma t1on by 6iv1ns stragglers' routes and rendezvous points relative to ~ertain reference points, the location ot which 

the Ge.rm.ans were unable to determinea During the remainder 

of th.e submarine oampa1gn against Atlantic c~nvoys the U-Boats 

ware obliged to depend on their own rec\'>lll1e1ssanoe and tbs t ot 

the few long ... 1·ange aircrat.t available. The Allies, on their 

part. 11 made reconnaissance by the U--Boats tl'iemselves very d1tt1cu.lt by air·o't'att pa tro.l.e~ thus to.rein& the u .. aoa ts to operate subme.rged a .large part ot tkie Mme~ 

TOP 
_ (LO) 2271-52 

SECiJR1W1~f{)~~M!R~ Deof¥tion Intelligence Available ~ Elie Allies ----

Tbe Allies began readi.ng the "Enigma" communications ot 

the German submarine force in December 1942, and G~tinued to 

read them spora41cally with varying delay times until October 

194), trom which time on to the end of the war, the messages we~e read Oilmpletely day-by-day, with n~ s1gn1ticant delaya 

The messages decr1pted by the Atlantic Section of Op-20-G 

are tiled b7 days. (~'he date or decryption was appended to the 

translation ot each decrypted message beginning on 20 February 194).) A complete tabula t1on :» t all decrypted .messages pertaiD- ing to the North Atlantic c~nvoy war, during the months of March, 6pr1l~ Mey, September 16 through JO, October, November. and December ot 194) and January, Februa17, and March ot 1944, is 

.presented in Annex 2o2. In addition. there is a tabulation ot al~ messages pertaining to u-Boat operations in the Atlantic 

nortJl of the e~uetor tor the period from l June through !; Sep- tember 1943· The messages are classified according to content 

and time ot delay in decryption. 

With respect to their contents, the m.esdages oan be included in three general groups: 

(1) 11essages. either trom. a U-Boat or from BdU, which 

give the present or prospective l)Osition ot a U= 

Boat; these are callee! type "P" .messages 1 n the 

table ot Annex 2o2o 

(2) Messages, chiefly trom BdU, which contain opera- tional orders to individual U-Boats groups ot 

U-Boats, refuellers, eto., designating 9atrol areas 0 

courues 1 refuelling rendezvous, eto. These are 

called type "M" .aiessageso 

()) Messages which deal with c~ntaots between the U~ 

Boa ts and their enemy o Froru Maroh to May l 943 they 

were pred~min.antly ~eports o-r contacts on convoys; 

trom June to 8eptember 1943, almost entirely re ... ports ot contacts by the Allies on U-Boats 1 since n~ oonvo7s we~e contacted during tnia period in 

the area mentioned. Fro.m. Cotober 194) to M-rch 1944 

the7 were of both kindso These messages are ualled 

t,ype 11cn.., 

A ((eneral idea ot the amount of" radto i.ntelU.aence made 

available to the Allies, and ot the delay in decryption time 

during the period l March 1943 to )l March 1944 is given b7 • 

tho tallowing grouping ot the deoryl)ted messages. Table I and 

Table II are arran.ged in three parts because of the ditterent 

TOP SE.CR ET \CANOE ~-4 
P~•C NSS-346 

(LO} 2271=52 

TABLE I 

Volume of Radio Intelligence 

Period II: l March - 31 May 194.3: 

Noo ot Percent Decrypted Within 

Month ~cr1etiof!! l day 2 days 3 days 10 days ...... Ot'"M" w ===--

March 839 121' 3.3,. 50;4. s~ 

April 76S 44/, 61~ 66" 82J' 

May 836 ~ iU ~ 88!0 

Total 2440 331' so--" 611' S4fo 

Period Ill: l June - 15 SeJ!tember 1~4~: 

2 days - ~ .!cO dars &~a~...! 

June 109 910 55~ 69J' 8Si4 

July 80 J ~ .. 211' )4~ August 67 434 67/, 88~ 

l ... 15 Sept. 31 l 71-P 781' - - - Total 287 6-/l 40/, S61' 70.,b 

Period IV: 16 SeRtember 194.3 ~ Jl Maroh l9~: 

- 1 day 2 dars 3 days ==-- 10 dqs 

16-.30 Septo 149 17-/o SB1$ 7~ 99/J 

October 287 6~ 12-,, 78~ 9610 

November so 71~ s~ 951' 10010 

December 99 83}b 931> 96~ 100,b 

January 1944 236 94~ l00JO 10();,4 lOC>fo 

February 294 87'4 97p 99A lOO;b 

March 202 12!.. 96L! w99i' 1Q9i - Total l.347 74~ 87-J, 911' 9~ 

TOP S E C R E T .CANQE 
pREFc Ij31 :jriiijiSj a 

u L '-.J .l.'- ..L ?°" 

(L0)227l-52 

SECURi"fV1iFORMAflON 

cono$rning the·proportion ot all Ger.man transmissions concerned with u-BOa.ts that were deor7pted 1 it was the rule that 

:'PtiC-NSS-)46 

if .messages on any day were read, all the tra.nsm.issions were rea~. From .Anne:x. 2oit it is seen th.at on certain days none were 

read within 10, or in the second period, 15 days.. The number or 

days in each month tor v&iich no decryptions are tou.n.d in the 

tiles is as tallows: 

ua.roh 1943 • • 0 • • 0 • 0 • 2 de7s 

April • • 0 .. • • • • • 7 days May 0 • 0 • • • • 0 0 3 days 

Jwie • • • • • • • .. • ta days July 0 • • • • D • • 0 l day 

.n..u.gust 0 0 • .. • ., Q 0 " 8 days September 0 • • "' . • • • D 8 de7e 

October 0 0 .. .. .. • • .. 0 o days 

November 0 Q .:. • 0 • .. 0 • S days 

December 0 0 8 0 0 D • 0 0 S days 

January 1944 • 0 0 0 0 ~ 0 0 O days February 0 .., 0 0 0 " 0 0 O days 

Maroh .. • 0 0 0 0 0 ., O days 

Concerning the character ot the intelligence obtained from 

decryptions, Table II presents a grouping according to tbe type of m.~ssage, as defined above. 

TABLE II 

Chara!~~~ ot Radio Intelligence~ 

Period II: l March_:._31 May 194~0 

Noo ot Decryptions ~pe ot

1

Messar 

Month !!ll!11n ).~ days . - - March 689 3~ l~ April 627 21 13~ lZ~ May ...m m l~ ii1 - Total 2055 29P ll~ 6(),(i 

Feriod III: l June ... 12 September 1943: 

wl th1n_l2 d!l;! 

June 93 44/! 42~ 141' 

July 27 ))fo 31 .. ;, 32;& August 59 36~ 49~ lS;l. 

l-lS Septa -

24 42;' 12.i ~ 

Total 203 35,-1 441> 21;& 

TOP s E c R E T LSANOE 

IPQ:p SBGBBIP 2-6 
'fef SEGRi'R 

SECURITY INFORMATION 

period IV,: l6 September 1943 .... 31 'M~rch 1944: 

'MOlltll Within 10 48{ s ppe o.f~essage 

c 

16-30 Sept. 147 22;i ·1s~ 60~ 

October 276 30~ 37~ 331' 

November 80 311' 39~ )~ December ' 99 47-J, 45~ Jan uarJ 1944 2)6 71*~ 1910 1°"'1 

Februar1 294 69*'/I 111' 2~ March 202 84*-;, ...M 

Total 1334 S4jJ 221' 237' 

*Nearly all ot these were weather reports sent by three u~Boats 

several times a dayo 

There is a great difference in the amount and the char ... acter of the intelligence in the three periods. The huge traffic of March t:> May was due t::> the mago.i tude of the oollvoy 

war oarried on during those months. Each U-Boat reported every 

contact and loss ot c~tact on a conv.;)y and BdU repeated it; so 

that during a long chase scores of SL\Ch messages might be sent 

baok and forth in a few days. This accounts tor the preponaeranoe ot type c .messages during this periodo During the SWi.\lller 

no convoys were contacted, and the few type C messages were 

nearly all reports ot attaoks on the U-Boatso The great deorease 

in 'li.o.e amow1 'ti oi- rae110 oomm.unioa tions during the swmner is 

explained pa~tly·by the lack ot o~ntocts on. convoys. and partly 

by the tact that in July the U-Boats were sent to distant areas 

to prey on coastal shipping! and maintained radio silence except 

to report attacks and posit ons when ordered to do so by ComS11bs. 

Starting on 16 Sspte.mbar 194), tlle u-Boats were onoe .more sent 

oaok into the North Atlantic, and the volume of messages in~ 

oreasedo From September to December, ~e emphasis on the type 

or .messages sent changed from a to P until by January! Februar1~ 

and Maroh. the preponderance or messages sent were ,pos tion re ... ports, and these originatea in large measure from three ur ... Boa ts 

which sent weather reports, two to three tilnes daily.. However, 

the positions ot practically ell u~Boats were known trom. the 

type M messages in which BdU gave the U-Boat position assignmentso 

The most valuable .messages were obviously the type Mo 

These c~ntoined important information involving groups of' U=Boats~ and ~~e patrol areas and movements of packs, refuel~ 

ling rendezvous, etco During the ~nths March to May over 200 

such messages were decrypted within 10 days, and about halt of 

these within 2 days. During the summer about 90 t7pe M messages 

TOP S~CRET CANOE 

.. -- / 
sECUffITTutNFORMATION cw> 

2211

-

52 

were decrypted within 15 days, SO within 5 days, and 7 within 

PR'liC-NSll:i-}46 

2 days; dealing, as they did, chietl7 with refuelling rendez.... 

vous, their great importance in the hunter-killer campaigns is 

obvious, as can be seen trom Part 4, where the manner in which 

these decrypted co.mmu.nioations were exploited by the Allies is 

discussed. During the last period (September 1943-Maroh 1944) the Y type messages were decrypted with such promptness and 

efticaoy that the Allies had current knowledge ot the .formation 

ot praotically all U-Boat groups, together with their positions, the areas they were to patl'Ol, and even the specific convoys they were intended t~ intercept. 

T 0 P S E CR E T .~NOE 2 ... s 
(L0)227l-52 

SECURITY INFORMATION 

). 'DU!i U'l'ILI~TION OF D&XlRlPTION IN'l'l!:LLIGENCE _, DY mm _____ _ -

The strategio use t:> which BclU pu.t the information made 

available to him b7 X-B intell1genoe has already been mentioned 

in Section 2.1. Thro&.tgb.out the duration ot the North Atlantic 

oon\roy war l1e .Pladed his U-Boat ,P&cks in patrol lines at the 

positions which, aooordiq to oaloulat1ons base; in 1 arge 

measure on decrypted allied messages, were o:>nsiste.ntly m.ost 

likely to be those ot greatest c:>nvoy density. When, in 

January 1943 the Allies first i.ntroduoed the s~uthern r~ute 

along the 406x-450N parellels,--heretotore shunned because ot 

lack of enough escort shigs to compensate tor t.be abs.ence of 

land-based air support for too long a period in mid-ocean--

the x ... :s service gave him. int or.ma tion ot the change 1 w1 th , tlle 

result that .be was able t~ shift the general ,Pattern of his 

North Atlantic u-Boat operations 1n order to meet the new con= 

dition with ver1 slight lose ot t1me: a u-~oat group was plaoed 

across the new route by 19 January, and two weeks later carried 

out the first maJor attaok ot the new year on SC llS which 

netted the u-Boa ts 12 ships su.nk. Wit.bin the next sl:x. weeks, 

this attack was succeeded by the attacks on ON 166 (15 ships 

sunk), !:IX 4t29 ( 13 sunk:) and SC 122 ( 9 sunk:), all in the s1m.e 

general area. . TaoticallJ, BdU was able t~ exploit the x-B intelligence profitably because the large ~uantity of ~rompt detailed inter.ma~ 

tion on specific convoys treque.ntlJ enabled him. t~ execute the 

movements required t~ bring the largest possible number of u~Doats 

to the attack. The extensive use he made of the X0 B intelligence available t~ him is evident tr::>.m a perusal ot tbe war Diary: during the period troa l JLll.J 194~ to )l May 194) one finds ~4 oases in which .b.e .mentions deoryptions ot Allied messages 

as governing his placing ot a U-Boat group in a definite patrol 

area t~ i.llteroept a speoitically designated convoy. ot these 24 

convoys 20 were contacted, with SS sinkings resulting trom. atd 

taoks on 14 ot tll8Jllo (These attacks included t.be three disas~ 

trous ones on SC 118 1 SO 1211 and BX U9-SO 122, which netted 

the u ... Boa ts 46 sllips aunkp) The .most dramatic example ot this 

s::>rt of tactical employment is towid in the pursuit ot HX 229 

and SO 122 in Marc.b 1943; a decrypted Allied message apprised 

BdU ot a diversion of HX 229, and he reacted so promptly (bf -cenoeliing an order ::>nly a few .hours old and directing a radical 

course change) that the Atlantic section of Op-~O-G (who read 

BdU0 s message promptly) were convinced that the Allied cipher had been compromised. (This particular combined 09eration netted 

t.be U-Boata ~2 ships sunlco) 

T 0 P S E C R E T CANOE 

3-1 
'feP SEeRl'l' (l.0)2271-52 

SECURITY INFORMATION 

"liNC-NSS-)• 6 

In the period tr:>m September 1943 to Maro.ti 1944, when B4U 

no longer bad good 1 AtelligeAoe available, lle t.r1ed to exploit the very scaatr gle&A1.aga to the utmoeti 1D. the lrar Diary he 

.mentio.ns l.-.d 1ntell1geAoe ill oonneotioa with 15 oo.uvo7s. Only three of tJlese were o:»ntaoted, 111 tih two attacks 7lelding 4 

siulcingso · 

,Preo1ae evalut1oa ot the operat1011&l etteot ot deol"J'ption intelligence ~qtd.rea o~.11aiderat1oa AOt o.nly of the successes 

obtained with 1~• "99, but ala~ eoae measure of the successes 

t.b.at wou.ld .bave been ob,a!Aecl w1thout1 t. 'l'hese "ueat10.11s are c~nsiaered 1A tbe following sections. Die straightforward etfec ts of us1D.g deor,gtioa 1ntell1genoe are expressed quantita- tively ill terms of t!le ab111t7 of the U-Boata: (a) to contact 

the oonvoys (Section 3.l); (b) t~ oonve~t the cOAtaots into 

attacxs (Section ).2) and (o) t~ sink ships (Seot1oA )o~). 

)ol• The Etteot ot x-B Inte1111;noe on the cugebility of U-Boata donEachihg a C nvol• 

Det1n1ti0Jl of ncontacta 

In this paper the term noontaot 0 ls used 111 t.b.e sense t.ba t 

a given convo1 is oontaote4 onl1 once, regaralesa ot the number 

ot U-Boats t.bat actuallJ contacted it. T.bia rule is adhered to 

even in the case ot a oonvoy that, ha•ing been once contacted 

and subse~1.1entl1 lost, was reoontacte4 later. 

:Qif1n1!1on ot "OO!l;Promise" ot a qonvol• 

A convoy is c.lnaiderecl t:> have been rroompromised" if there 

was x-~ 1ntell1ge11oe available o:mcerning it.which! according to 

tbe criterion described in section a.1, wes potent ally useful 

to BdU, whether J1e u.sed it or not. A oompromised co.nvDy speci- fically mentioned as being si> in the BdU war Diar;r is said to be 

"design.a te4" by Bau. 

Data tor sections 3.1 and 3.2 

Tne basic data required tor the computations 1D Sections ).l and 3.2 are tabulated in AIUlex 3. Data on the status ot X-B 

intelligence and ot action by BdU with respect to particular 

co.nv:>ys are tab1.1la te4 111 .Annex. 2ci l. 

'feP BB0ltn 

TOP s E c RE T ft&UOC--

&-.2 \j.ftl'fV .. 
SECURITY INFORMATION 

) .1.1.. Etfec·t ot X-1-} I.ntell1genoe on probaoili ty of Contact .. 

(a} overall probab111t~o Table III is a swumary showing tha average· gr~ha6111ty o a convoy being contacted 

when it was comprO.cDised by x-~ intelligence, and when not. 

TABLE III 

overall Etteot ot X-B Intelli§ence on Contact 

-.... -m te or u-Boa ts on convoys 

------~------------------ Nlunoer of Conv~ys in Area ••••••••••••••••••••••••• 266 

Number jf Convoys contacted ••••••••••••••••••••••• 91 

Number of Convoys not Compromised by good x-B ••• &. 168 - Nwaber of Convoys Compromised by good X•B......... 98 

Number at con tacts o.o. non-co.mpro.m.1 sed conv o:>ys...... 43 

Number of contacts on Compromised Convo1s ••••••••• 48 

overall Probability of a convoy being contacted .... 34;& 

Average Probability of a non-Compromised convoy being Qontactea ••••• -::7 •••••••••••••••••••••• 26~ 

Average Prooability of a Compromised Convoy being Contacted •••••••••••••••••••••••••••••• 49~ 

The date. in Table !II indicate that the average chance of 

a convoy being oontaoted 'Nh!le traversi.c.g the No1·th Atlantic 

vu1s nearly twice as g;.·ee. t 1 r BdU bad good X-.B intelligence 

speci:f.icaJ.ly on it. · 

{b) ~ne Probability or contact per convoy Day aer ]:;~~nay;-· p 

It is al'3ar tba t the averages just given d;, not provide 

an accurate estimate or the effect of good X-B intelligence 

on u ... Boa ~ perf'ormance, since they do not take int::> account the· 

extent of the U-Boat effort nor the number of targets in the 

PR~C-NSS-3'6 T 0 P 3-S E C R E T GANOE-
!0P SB6RE'f (L0)2271-S2 

SECURITY INFORMATION 

area. 'l'llis •Y be done, at least ~rudelJ, by COJD.putinG the 

prob2bilit7 ti.bat a aJ.ngle U-Bot1t would oo.ntaot the OOllVOJ' per day ot its transit; this quantitJ is the quotient or the nuaber of contaota 4ur1Dg a period 41v14a4 bf the product ot the 

number ot oonv01 da1a and U-Boa1; days 1D the area. When this 

is done, it 1s fOWld 1;Jlat tJl• avezage overall probabilit7 that 

a convoy woul.4.b8 ocmtaoted per 407 ot its tr&Jlsit of the area 

per U~Boat d&J ls Oo09~ when oompro.adsed by good X-B 1ntell1= 

gence 1 compared witJl a probab1l1tJ ot o.OSISJ', approxilDatelJ ;/3 

as great, wben not ao OOJllprOJD1se4. S1gnit1cant as this increase 

in convo1 jeopardy 1s1 it still does not retleot the tull use~ 

tulness of t.be x-B 1nsell1genoe. Tb.ere were other taotors tllat 

materially attaoted the ability or the U-Boats to utilize x-B 

intelligence ill oont&cting convo1s, the effocts of which cannot oe expressod quant1tat1ve11, but tend to .make the apparent value ot the X-B intelligence less than tb.e actual val~e, when 

a statistical esti.mate, suoh as tJ1e one given here 9 is attemp- tede These tt..otora are the following: 

(l) The weather. In some oases the U-Boats tailed to 

contact convoys ot Whlob BdU had good 1Dt~lligenoep and to 

intercept which he disposed his paoke across the route the 

convoy actually tookl because of weather cond1t1onso Heavy 

seas reduced tJle mob litJ of the submarines, so that they sometimes tailed to .reach a prescribed 9atrol line in timeo Snowstorms and heav1;. ).~ng-end~ing toga otten redu.oed their ability to sight targets; ill several oases a convo7 was able to 

sail direotl.1 through a patrol line without being contacted. 

This factor is trequen~ly mentioned 1n the BdU war Diary durinf 

Period II (JanuarJ - May 1943) 9 when the Germans·had the best dec~yption 1ntell1geAoe on convo7s. 

(2) The limitations ot U-Boat operability. In order to 

realize the full oapab!litltes or the ~ype VII C it was neoes= 

sary to refuel it while· on petrol, and so it happened ooca~ionally that even when BdU had very good information on a partic-. ular convoy, he had to torego pursuit of it tor logistic raasonso 

(3) The Ger.man princi,le or mass attacks. BdU was convinced thal it was more pro 1Ea61e to attaok a convoy witll as 

.many boats as could be homed onto ito Hence lt happened f1·equently that even when he had good X-B on several c~nvoya aur= 

ing a Eiven 1nterval1 so many boats were in pursuit or one or 

even more other convoy~ that had already been contacted, that 

it was not practicable to allot any boats to search tor the remaining ones. For example, in the attack on ONS-S in MaJ, 40 u~Boats were involved, leaving hardly any available to attack 

other convoys on which BdU had good X•li, tor a week or more. 

This is not to aay that the U-Boats oonslstently contacted as 

T 0 P S E C R E T&AMOE. 

!f'<W ~~T 3-4 
(J.0)2271-52 

SECURITY INFORMATION 

pq HC-HSS-34 6 

•111 GOllYOJS as SdU clee1red. From t..be v·~ear D1&rJ 1t la evident 

tbat tne1 a1aap,~1nto4 ddU repeutedl7. 

TM g.rlaolpl.e of o..,noeAU'&tl.;m ot U/11 a ud-.anoecl in ptAr~~-­

gru·pJl (J) &al).:JYe, i1l"a cY1denoe au.on a• y.as cJ.••n in t.Ae exa.nple ln tba' para£rapb ·~~eata ~t ~here ,,., aave bcea 1nter~als 

ot tJ.M cl"11'1Dg wulon JldU lwd sood l•B 1Atelll&•Aoe tor a nwnuer 

ot c0Avo1a 1n e1.oe~• ot tue AWILber wn1co 111a u/a• • oou.ld attaolq tbat 11 to sa1, W'le aaowit ot 1nt.ell1LeAoe available tor use haQ 

aaturaGect tlle tua~ .... 1t1ee tor "18lllt ltu 11· tbe U/8 tleet were A~t eatur~teQ wltJ., 1ntellieeuoe in th• aeose deaor1bed here, 

tbeA ao 1Acre~oe in the &Jll0'4Dt Qt aco~rate anu t1••11 1•B aecryp- tioae ad.gilt be e~peoted to increase th• rate w1tb wh1oh U/B'• 

oontaote4 o~n¥07a. Whetner ~r not euon 1at~r&tlon.oocurred 00Asistea.tl1 will now be investit;;1:1 t.ed. 

).l • .a., T.be "Contaot coe1·r1c1e11t" and "Opera t1onal ~'Wee,era te." 

A Metlat.are or CJ-loa~ pertormanoe t&it 111 some reepeo(s la PLOre 

aieanlnctul tnan. ~ia.ple probf.lbili t7 ot oon,aot. ia the "Oper& t1:>nHl 

sweeprate." The toll:1wlne 1s a brief disou.saioa or tbls quantity and or its appl1out1on to ~oe a1t~at1an 1A queotlon. 

The Dl.Ulloer ot oontoo~s that tne u-aoata o~~ld be expected 

to make durine ~ u-aoat da~a ot r~ndom seuroh ettort depends 

on tile tare.et uene1 t7 during t.be time interval in <tUestlon; Lha t 

is 

( 1) 

wile re 

a number ot oontaota 

H nwaber ot tarsete in tbe area 

A the area sea~ohed (aq. miles) 

T aearohing ettort (U•Boat da7s)o 

BJ 1ntroduo1ng a prop~rtioualltJ ooetf1c1ent, ~. ~ne ~ets 

(2) C="Q. <R> 'l 

The ooett1o1e.a.t ~ w111 be designated "ooa~aot coett1o1ent"• It is 1mmed1&tel7 apparent that lta .magnitude 1n41-

oates some weaa~re ot the u-Boat•a ab111t7 to contaot targets 

apurt tr~m Llle aensit,y of tarcets and the uaaga1t~d• ot the searoD. 

eftort. 'l'he dimensions ot "" are "area/t1me", sug£est1ng a searob. 

rat.e. In u oaae in wuioll the targets aa4 the aearohere are po- s1t1oAed at random but with a un1tora denait1 over the area, and 

the movements ot the aearo.b.er are independent ot those ot the 

target, ~ would be tJle true "sweep~a~e" ot tne aearober aca1nst 

T 0 P S fi-C R E T GANOE · 
' \.&.I ·· o } ,;;.,; ,, ')•r· • .A · ..... ,, · . ., 

The valwe of q, can be estimated from .it&"l:>vm capsbil1tles ot 

the seari::uer3 s cleteot.ion means (tile ••err~ctii·'le det-ec.tion rengs"t 

or the "swcepwidth'') ana the speed of the search rraft relative 

to tnat o! the t&rget.. 'fhls is sometillles aalled a. 11 theoretical" 

sweeprate t.o u1st1no1ish it. from. tt1e \<. computed fr~m aotllal. oporat:l.:>!laJ. .rssv..ltc;; tuat ia~ whoti ti k.u4.)YfD. numbe.1:· o.r oontact-s, and 

a renown -lr aseuuied te...:·t;et density are su.b..;ti t.uted in equa t1on 

( 2) ,, 1'.tl.e lat tor is oa.lleJ t,ne ••opere.tion.al'r sweepraea., 

. The condition of unif{>rm di.strlbution of tacgd~8 and 

searchers was never entirely me~ 111 ~ Ba~tle ot the Atlantic; 

althout:)l tne oonvoys were distributed fairly evenly and their 

average nwnber remaine.d nearJ.7 ooostant for long periods, this 

was not true of t.ne U-Boats. Exoept when transitinge the u-Boats 

were generally concentrated iD. packs, with t~e excepG1on ot a 

very few boats oper~ting independently on special missio~~L As 

a oo.o.sequeneet et any Given time" cert~!n portions of tne ent.lre 

rec.,lc-n were beinL .m.:>.re thoroughly swept .:sver than othersa 

With respect to the mutual inoependenae of searcher and 

target moveme.utsri t1~1 ... condition would be approximated a·t such 

times as neither aide had reliable k.nowledgs of the opponent~~ 

moVelllents=a ao.ud11i1on wl.l.i.oll occurred only sporadically during sllilrt intervals in the peri.od considered,.. 

In view of the restrictions ~n the definition of "sweep- rate'~ req>..11red by t.lia t..beory of searcl".i., and the conditions under 

ys!l.ich the convoy b~ t.t.le of the Atlantia was fougb..t 0 there is a 

valid ooject.io.n to u.si.ug this term, as oow.pu.ted l':r..>m. the oper·~ 

ational d£ta~ to describe the effectiveness o! tne·u~aoatsn 

For th.ls reason the te.rm "contact ooetficient" il.as been introduced to rep.lace "Operu tional sweepra.te"" It will serve as a 

u1easure of.' the ae.pttbility of tne U-=·Boats to contc.ct con11oy.s 11 

en.a. lihould reflect tb..e etfeat of intelligence on tneir search 

Ol'\,Pt\lJ.ilit.y., It &pp1·o:xi.ai.ates a true operati.:>nal. sweepwidth t.:> 

t.he e.x.t.en.t that tho com.ii t..1.ons :.>f u.nif'orm rauaom dist1·1ou.tion 

and independence of m.0·1e.ment are w.et ... 

(a) The true oper~tional sweegrate~ The close~t appro2~ 

lilllition toc'fle true 5Perotionar$wecpraEe of' the German u-Hoats 

ln the Batt.ta 01· t.n.e .t-i.t.lantic would be obtained by C'lns1der1ng 

only tnose convoys not. com.promised oy X-B in.tellit;ence du.ring 

a period when the ,~llies had t.he leest amount of intelligence c~ncerni~g U=Boat movements. The latter condition oecurr$d in 

.Period I, (f'r:>La July 1942 to December 19421 during whio.h tlle 

Allies were .not reaa.ing the Ge.rm.an oipher (except for the last 

days in Decem.oer)Q on the other hand, 63 out of 100 convoys 

were 11.:>t compr~'td.sed. by X-B 1ntc.=slligence-a good··sized sample .. 

PllllC-NSS-346 

TSP SI!i0Ri1.C T 0 P :s S E C R E T <. · --tlE 
0 BF fl?t-!l?-5~0E ,, r ~.c~n:: 

T~ S!!Cftk'f (L0)227l-52 

SECURITY INFORMATION 

Du.ring Period I tJle contact ooetf icient on non-compro~ 

mieed convoys was 24)0 sq. miles per da1~ This q~nntity is thus 

the ~l~sest approxi.mation to the ~ru.e operati~Wll sweeprateu (For detaila or tne ooaputetion see Anne1 )~) 

The rweeprote is given by the product ot the relative 

speed ~f searcher with respect to the target by the "sweep~ 

widt.b." ot t.ile searcher ... twice the "•i'fective range" ot d.etec··· 

tiono Using a reletive speed or 10 knots, the ~450 eqo adlesper ... day- swe-:,prate wou.lc'. correspond to a sweepwidt.tl ot abou.t 10 

.miles9 Oper~tional data on sic)ltings by Oilr own s~bmarines in 

t.b.e ?aoitic on sinele merchant vessAls gave a day-and-night average sw6epwidth ~t li ~iles tor a surracea sub.marine; on large 

oonvoys it sllo11lcl be su!>stantiall.y more: theoretically propor ... tional appru.xim.ately to the cube root of tbe number of ships in 

the convoy c (.Reference ( 1) ,, p.. 101) ... 

The contact ooef1'1c1ents f'or .Periods II (Ja.nu.a1•y ... aita7 1943) and IV (September 194) ~March l944)e comp~tea tor only noncom~ 

promised con~·oys, are respectively l.400 end 1550 square .miles-

.P•1·-aa7., This Gecrease from tile fisure tor .Period l reflects 

the ef:t'cct of the superior intelligence obt-ainod by tlle Allies 

through decryption inZelligenoe: during Period Il they read 

the Ger.man co.mmunications with consid&r£ble success (see section 

2u2); and during Period IV completely and currently~ This enaw 

bled them to dive.rt convoys around the U-Bt>et packs and was in~·· 

strwnental in I'e·luclng t.u.e contact coe1,tioi,ent trom )0 "" 40 per-= 

oent"' 

(b) Variation of the overall value ot tbe contact co~ 

efi'Iolent=ana correra'tiQZ& \';m·ene" extenE or X:-lf-in 

l'hte!!igencec· ·J!h& overall value or Elie con£ac( ooef ... .t1c1e.:i·t throughout tfie t.b.re3 periods., calculated from equation · ( 2) by insert1n~ the total number 01• contacts on all convoys& ti.;e total nwnber of u~:aoat dafs in the area 8 and the overall average nwnber of convoys in the area~ is 2350 aqo miles per day~ It 

will be noted that this number is almost equal to the closest 

apgrox.Laot1on to ~he true operational sweepratep which was 2450· 

aqo miles per dayo 

In general, the effect ot X-B intelli~ence on speoitic 

convoys du.ring given intervals should be reflected in the value 

ot the contact ooe1'ticients tor those intenuls.. For .. it during 

a given interval BdU .bad speoitic 1ntorm~t1~n on enough convoys 

to lceep -bis fleet occupied b.V t..b.ese alone,, the C'lnttict rate dur0 

i~ t.b.tit lu!"t~rvt.l =·houlu bo c..reiite.c t.n.. .. n du.ri.c.~ ~r~ int,ervt.tl in 

which the U-Boa ts Jlad to depend more on their own reconna1s·~ 

sanue and on BdUts @Uessing; since, in the former casey the 

U-Boats could presumably be ho1ned on to the target~ or enabled 

S Ea!? R E. TOANOE 
0 ffF e;Dt;Aj-l?iJO (L0)2271-52 

considering the three periods studied, the relat10ll beQ 

tween the overall contact coettioient ~ and the amount or good 

X-B iatelli~enoe \e as shc~n in 'l'ftble lVo 

'l~LE IV 

variation of overall contact coeffio1e.ut and Extent of x-B In- --- - te!l!gence by Fel"iods 

Period 

Io July-Deco 1942 

IIo Jan-May 1943 

-

.. . 

/, of 0011vo1s . _ . 

Compro.mised bl x-~ 

.o.,eral.\. QpJ:l~Ct · 

uoe-.rr 101"""" 

2650 sq •. m.i./d.ar 

2050 n 

IV~ Sepu 1943-March 1944 1700 .. 

The lack of oorrelation between the overall o~nte.ct odetf.ioient and the extent of intelligence on conv~1 movements might indicate that the saturation eZtect mentioAed earlier in this 

section really exists; but it could be due to a generally lower 

effeo ti veneas of u ... Boat search, as a result of Allied COUJ1.termeasures9 weather, etco The saturation efteot would be a1~1-

ficant especially during Period II, wh.eA BdU bad available good X=B 1ntsll1genoe on 75~ ot all the oonvofso The low val~e ot 

t.lle cautaot aoefticient in Period .n- probably represe.uts the 

etteot of the superlatively good Allied intelligence on the true 

operational sweeprate of tbe U-Boats. 

The variatiOll ot the oontaot coettioiellt and extent ot 

X=B intelligence tor intervals ot one month is shown in Table 

Vo Fig~e l shows this variation sraphicallJo 

TABLl!, V 

Monthl{ variation in'Extene ot X-B Intelli§eDce and 1n tb.e 

·aontac dOifric!ent - ·- ·-

Pe1•iod Io 

(Allies had no 

Dacryption 

·1ntelligence) 

PllllC-NSS-,U6 

'i'GP SE0R£T 

overall 

-1' ot co.ntaot 

compromised coet'tioient 

Month convo1s ~qo Mio per - -

July 1942 )9" 1450 

Augo 47-/. 30SO 

Sep. 37-k 2100 

Oct. l)p 2050 

Nov. 43~ 4SSO 

.Dsco 441! 2400 

T O P :s-'6 E C R E T CANOE 

Day) . 
1'611 SiS RiS'!' (LO) 2271· 52 

SEUUHllY INFOrtlVl/\TiG~"~ 

overall 

;, ot Oontaot 

Compromised ooettioleAt 

uontb. COAVOf 8 ( SQ.oMi o per Del) w 

Period IIo Jan. 1943 6)~ 2)00 

(Allies read Febo 4Sk 1950 

Messages Maro 93i' 1700 

Partially) Apr. 65~ 2600 

Mal S~i 1900 

Period 1V ~ Sep. o" 2400 

(Allies read. Oct. l~ 1150 

ussages c~re.utlJ NOVo g~ 15;0 

ano completelJ) Deoo · 650 

Jano 1944 O.J. 2300 

Feb. g~ 3500 

Mar .. 850 

A turther breakdown ot Per1o4 II into lO-da7 and lj=4a7 intervals Shows a similar lack of correlation. lt is not oon° 

eldered necessary to include thes~ resu.l ts in this report .• 

(o) Comparison ot ooataot coett1o1ents computed tor ooagromiaed and R,on-doau2r0ilsed aonvoys. 

The average value ot the contact ooett1c1ent tor the three 

periods ill question, considering on.11 Aon-oo.mpromised oonvo7ep la 17'0 sq. mi. per da7. The average value of tlle oontaot coe1'f 1c1ent, aOAa14er1ng o.al.7 tJle ooaprom.iaed convoys, is 2850 sq • 

.m1a per 48.J. It thue appears.that tbe immediate etteot ot x-a 

intelligence was to raise the oontaoi ooetf1o1ent to about t1vetll1rds tlle normal value. Just as 1n the case ot oontaot proba- b111tJ discussed above in the preceding section. 

When the three periods are considered separatel1, the figures show.n in Table VI are obtained.* The oontaot ooett1c1ent 

on non-oompro.mised oanvo1s is 1.a.d1oated by "°; that on oompro- .mised O:>DVOJ8 (that 181 tnoae OD ~hioh good X•B intelligence 

was available •. whether or not used bf BdU), bJ QJ.• 

'1f the oontao6 ooett1o1enta are co.mpute4 tor .monthl7 periods, it is found that the 1nd1v14Wll values tluotuate widel.Ja (S•e Annex 3, Table 4.) In the case ot tho non-eomprom.1sed convoys, the range is from O to 5190 sq,. u./da7; 4ur1q halt the months 

it was between i;so an4 2450.sq • .caio per 4a7. In the oase of 

the compromised oonvo1s 0 the range is trom O (in December 1943, 

wlth onl1 one coaprom1sed oonvo7) to 5100; half the values lie 

between JOOO and )800 sq. m.1. per clBJ~ 

PROC-•SS-JU 
-

REF ID:A65650 

1'186 l MonthlJ' varJ.at;ion 1D Extent of X""B I.11tell1genoe and in Oontaot oo~tf'ioiento 

------- -/, ot Comproadaed Convol'So 

Allied neor7ption Intelligenoe 

---Contaot Coetfloie~t, Q.1 Bqollieper 48l'o 

1942 fr= 

Oot 

sap NOV Jan 

1943 

Period 1·---l.). I* 

Hone 

J'eb Bov Jan 

11a1 Ooti neo Feb Apr 

1944 

Period II....,..··~~ ..... ---Period IV---...f 

Partial Complete and current .. 

"i' " 

.. 

. .. 

I 

~ 

II: 
Average t~ all per1o4s Period I 

Period II 

Perlocl IV 

fABJ& VI 

.iA 17SO sq. IAi./da7 

2450 1400. 

1,50 

(I.0)2271-5~ 

as;o sf. mi./ daJ 

29,0 

2350 

405~ 

•Tun weN o.a.i, tour oases ot oomproaalsed oonY01a dur1Ag Period 

IV; three ot these were oontaote4. . - . statiat1oa1 anal1s1s ot the 4au 1!l 'l'able VJ: (ob1-aquare4 teat) 1n41oatee t.lla' tlle 41fterenoea betwe8Jl tbe sweep-rates 

on non-oo•prom1ae4.Nn4 ooa~roa1sed oo.uv~ys are a1sn1t1oant. 

It bas been mentioned that a possible reason tor the lack 

ot correlation between the degree of X•B 1ntell1genoe an4 the 

oontaot ooettioient is the tao~ that during Periods I and II 

B4U generall.J had sutf1o1ent x-s intell1genoe on oonvo1s to 

eu.ble .b.im 'o aaneu:ver hie u-soate to attack oer1ta1n oompro- a1ae4 convo1a, 1gD.or1.Dg others unless bJ ollanoe t~er ottered 

a sood ogportu.a.1t1 tor attaoto. TAere 11 oons14erable ev14anoe 

tor this in '11.e BdlJ war D1a17. It this hypothesis 1e oorreot, the cOAtaot ooett1o1en~ tor auoh designated oonvore should be 

aubstaD,1allJ greater than the value ootained bJ oonsiderins 

all comproa&ised oonVO)'So This ia aotuall.J the oaaea I1l Per- · 1o4 I, ) of the 37 oomproa&iseel 00i.tvo1a are a.pa o1t1oally 4es1pate4 bJ BdU as l1av1n.s been so oOJRproaaJ.sed; all 3·we:re 00.11-

taotedo IA Period II, B4U mentions X•B intelligence 1n oon~ 

neot1on with operations attain.st 21 OOAVOJ'S (ollt ot '1 that 

were oo.mgro.m1sed); ot these 21, oontaot was made on 17 o In 

Period IV, whert %•B 1Atell1genoe was almost non-exlstent, onl.7 

4 convo7s were oo.mpro.aa1se4, and B4U des181l8tee all tour ot ' 

these tor operations; 2 were oontaote4. The oontaot ooett1-

o1ents co.mgute4 from these data ars ab.own 1n Table VII; the1 

&1'8 calle4 Q2. ~he ooett1c1811ts pertal.D.1.As to those oo.mpro- mlse4 oonvo1a not 4es1snate4 by BdU, and to 11011-oom,promlaad oonvo7a 1 ~l an4 Q.o respectivel.J, are 1nolu4e4 tor oomparisOAo 

TOP S-BCR.E TOANOE 
• 

c l'C 

TOI 8ECHE'f (L0)227l•'2 

SECURITY INFORMATIOL m 

oontact coett1c1edla OD Conv11s De81gn&ted bz Bib f af 1

a1efliloni oh t Aills of I i-_ X§t;XJ\i§AO• I I 

. Q, 

period ( SQ.oll1 ~/DaJ') ( &cloM~? /f/11.1) 

2600 

16~0 

( SqoJd.~/JJ1J) 

24SO 

1400 

1700 

I 

II 

IV 

8400 

)400 

4050 (a) 

A.vezase tor 

All Periods . 4450 2050 1750 

(a) Ho oonvo1s in this olaes 1n Per1o4 IVo 

IA spi'e ot tb.e small samples 1A Periods I an4 IV ot des• 

ignated oom,proad.sed oonvo7s, the ditterenoes between Q2 and Qo~ 

and between ~ and ~. tor all t4e periods and tor the average 

ot all periocls aro a1galtio1:.nt wltllin 9"1& oont14enoe limlts; · tha~ is, there le at the moat a 10~ o.b.anoe tlla.t the ditterenoes 

.mentioned are 4\"!8 to ohasioe tluotua.tiona. T.b.ue ~t appears t:tom 

tlle data ellown in Table VII, t.bet the value ot l•B 1ntell1sence 

to the u-a~at oammand oan be awamed up as tollowso The information obtaJ..Ded on apeo1tio oonvo7s enabled BdU to seleot certain ones tor paok operations, either 1snor1ng others or leaving their 4eteot1on to o.baAoe. A.a a raault, the ettect1veneaa or 

tJ:Le u-Boats 1A oontacL1ng oonvors was 1Aoreased to about ·2i tiales 

the figure when no X-B intelllgenoe was available, and to about 

twioe t.hat OA 0011'Vo7s whioh, tD.ougll ooapromised b7 X•B !Jltell1 .. sence, were not sgeo1t1oally seleoted tor operationsu 

).2 !ib.e Ettaolalt x-s ID.telligenoe on the Attaok Factor and the B lng Aateo • 

In general, 1A evalwating tAe etteot ot 1Atell1genoe _~e 

00J1taot rate 1a a aore aign1t1oaat quantit7 tban the sink;uig · 

rate, s1noe there is no direct oonneot10A between 1D.tell1genea and sinlti.11& rate. TA8 s1nk1ng rate 4apezi4a directly upon the 

contact rate, as well as upon other taotore which .have no oonneotion w1t4 1ntell1genoe 1 suOb ea tire ooAtrol, araw.ment, ag- greasiveneaa, eto. on the part of the u-Boa,, and on the etteotiveness ot ant1·a~bJDar1ne aeasurea on tAe part of the aeteAse. 

However, 1l1 view of t4e taotios em.plo7ed b7 the German 

tJ-Boat oommand or veotor1ng evel')' B~a1lab·le u-eoat to the attaok 

on an 1.Qteroepted oonvo1~ it see.ma reasonable to preewae that 

the p~asess1on ot good x-s 1ntell1seaoe wauld aaake it possible tor BdU to dispose bis boats in a manner that would not onl.J anhAnae their o.b.alloe ot contaot~g e oonvoy1 b~t also ot converPRNC-NSS-'U 

~OP Sl!iSR!.1.' T 0 P >i~ C R E T OANOE 
!OP SEC!ZT (L0)2271•52 

Sf£ltttf t.'~!P.~M~~1l~Nattaok aa well aa uabliAg Ab to 

vector larger nWllbera at boats to the attaok, and thus obtaln 

a greater silllcln& rate. 

Table 1IlIA preaeA'• data s~ow1ag the effect of X•B intel· 

11gence on the attaok factor &Ad tille a1Dk1Dg .rate. only 'hose attao~s tha' 71elde4 at least one a1Dk1Dg are oona1dere4. 

It mi&tlt be argQed t;.nat a more raal1at1o apgroaoh would be 

to consider onl.J the attacks of aa~or proport1ona; i.e •• tihOee 

wn1oh res\llted 1n aLLltlple kills, in view ot the arsuaaent o1te4 

above f~r the uae of t.b.e elnlein.g ret.e es a measure; t~r ot 'he p5 auooesstul attacks, halt resulted in 0417 one or t~o silak1Ag1 0 ao.d tllest1f'1Aolu4e so.me oases 1n wlloih on11 one or two U•Boata 

oontaote4 a oonv~1 aa well as ~wo oaaee whioh the Germana ooneidered 1A4epen48Jl,s. Table VIIIB·glvee the figures tor attacks 

that resu.lted 1D tlU'e_. or a10re s1llle1Ag&o. .. .•. • ... . . . 

Till§ VIII 

Etteot ot X~B iltelllfenoe on Attaok 

tao£o! an Bihl E1 Rite. 

Non-coa- Coapro- promiaad mieed 

QOAVOJ8 Oonvora 

Ao All ,Attaoka with at least one S1D!C1nl 

NwD.ber of convoys 168 98 

Number ot ooataota 43 48 

Attaoks 29 J6 

Percent ot Convo1a 

AttaOked · 17'/I 'J7-/J 

Percent of COD.tacts 

oonverted to·· Attaolca 68~ 751' 

Number ot Sblps SWlk 101 162 

Average Nwnber of Ships Sunlc per Attaok 3.5 4oS 

Peroe.nt at ovenll . M~*s 4~ 5~ .Perout ot -ovol'llll 

S1nk1ngs l8~ 62~ 

Ooapromiee4 

00llYOJ8 

Deaigna ted bJ B4U __ 

28 

22 

16 

571' 

7)/, 

89 

So5 

overal.1 

266 

91 

6S 

'U+(. 

2Z~ 

4o0 

T 0 P '°S'E C R E TCANOE 
·.eop 619ili'1' (L0)2271-S2 

SECURITY INFORMATIONwn,. vm (Dtod) 

PONC-NSS-346 

ltteot ot X•B IAtelllgeaoe on Attack 

fiotor ihd !1Bii111 tat&o ' 

comprom1se4 

Convo7s 

Non-coa- Oomp.ro- Desig- .Pro.mlsed .miaed .raate4 

oonvoia Oonvois bz BdU. overall 

B.-i Attaoks with 2 or lore 51D!'1A18 

Number ot S\loh Attaolca 12 19 9 31 Percent ot Oonvo11 Attacked 1/1 191- )21' 12~ Poraent of contacts 

converted to &uch Attacks 

1\:1\lalber ot Ships SWl1c ~r J~ 4li& 34~ 81 219 Average Number o~ Ships SWllC ger Attaok 605 1o5 ~oO 

Percent ot overall 

Attaoks 3~ 61" Percent ot overall 

Si.Dld.ngs 36;. 64,6 

oona1der1ng all the attaoka (wit.ti at least one e1Jlk1ng) 0 it appears that tJle ava1lab111tJ ot x-s 1l1tell1genoe Jlad no apprecia~le etteot on the at,ack factor (peroent of contacts 

converted to attacks), wh1oh was near 7(}/J in all oategorieso In t.tle oase ot ma~or attaoJcs (3 or more a1nkings) 9 tb.e attaok 

factor was nearlf 16 times ae great tor compromised deaigaated convo1s as tor non•ooaprom.lsed an.eso fh1a mJ.gtlt be taken as 

indicating that the poaseasi~n ot good intelligence was ot sig- nificant aas1atanoe to BdU in disposing ot his U-Boats eo as 

to enbance their ohanoe ot making a maJor attack~ 

Witb. respect to a1nk1ngs, 62~ ot all s1nk1Jlgs, as against only ;)~ of all oontaots, were trom oomproadsed oonvo1so This 

results 111 a hi~Jler average AWlber ot snipe sWlk per attack--

4 oS from compromised oonvo7s oompare4 with )., from non-oompromised oa~so In the oaee ot the oomproalsed oonvo7s desig- nated b7 BdU t.tie average Awaber ot s1Alc1ngs is s1gn1t1oant11 higher than ln the oaae of the non-compromised oonvo7a, both 

when all attacks and also onl7 the maJ'1r attacks are oons1dei-ed., 

Because the state ot attairs wi~h reageot to decrJption intelligence on both e14es 41ttered so greatl1 during Periods I~ II0 and IV9 1t ls ot interest to oompare the etteotiveneaa 

' . 

T 0 P S 3fu.C R E T\CANOE 
:c·er s1;e1&! (L0)227l-S2 

SECURITY INFORMATIOtJ 

or tlle ave.rage u-Boat or tbe tAree 9e.rioda, as .measured in 

"R•C-•Ss-3•6 

terms Of ships SWllc pel' U-Boat•487 ger OOAVO:y-dayo ID fable 

xx the vel~es ot the 0011taot ~oett1o1ent an4 t.tle s1nk1ng rate 

per u~Boat-dar per convo1-da1 are expressed as ratios ot the 

overall values tor Period Io 

Psr1o4 

I 

II 

IV 

·TA.Bl.I .I! 

C(!!DR!rieon ot overall contact and 

§!iltg @Ci!i I 

Relative 

ooa.taot 

coettioient 

loOO o.1s 

Oo64 

Relative 

S1n.k1ng a..te 

per t1•Boat-Da7 

1.er OOAVOJ•DaJ' 

loOO 

1009 

OolS 

It is aeen that, wl>.ereaa the abilit7 ot the average U•Boat 

to sink ships from convors was reduoed to near11 one-six.th dt.U'• 

1.ng Period IV, ooagare4 wit.ti 2e~1ods I and II, its ib!Iili to 

contact the oonvoys was reduoe4 to OAlY about two-thirds ot the 

previous t1gu.re, ill &Jite ot the almost complete lack ot X•B 

intell1genoe during this period an4 the completeness ot Allied 

deorypt10.U.8o 

caution aw.et be oDaerve4 in interpreting these figures. 

on the one han4 1t 1~ not oorreot to conclude that the reduction in the oon!eot rate was due entirely to the status ot the 

intelligenoe on both sides 4ur1Ag Period IV. It is equallf incorrect to oonolude ttiat tne reduction in the sinking rate must 

be ascribed entirelJ to ~he increased ettloao7 ot o~her antisubmarine measures, aa14e rrom the reduot10l1 caused b7 the decrease in the oontsot rate. These are overs1mpl1t1oat1ons. It 

has been pointed out above w.tly the contact rate itself does not 

retleot the tull value to the Geraiens ot the UPB intelligence available to them; &Ad in Part 4 ot this report 1~ w1~1 be shown 

t!iat it ls dittioult, if not 1.m.posa1ble, tQ evaluate the complete effect ot Allied decr7ption 1.Ate111genoe on tbe ettectiveness of 

the u~-soa ts. 

on the other hand, it is equall7 necessary to repress a 

tendenc1 to ascribe the collapse of the German U-Boat ettort in 

the winter of 1943•44 almost ent1rel.J' to the 001141t1ons ot deoryption on both sides, follow1a& a i!!l hoc· propter hoo reasoning process. The part played bJ e-a-aeoryptlon-ni the 

decrease ot U•Boat etteot1venesa attar Ma7 1943 is discussed in 

detail in Pa~t 4o 

T 0 P S:Ji C R E T GANOE 
~L"' SISS!l' ' 0 'f¥F s1E\;esrft ~LO} 2271 ... 52 

SECURITY INFORMATION 4. '!HE VALUE OF DECRYPTION INTELLIGENCE . . TO 'l!tlE AttIES • I 

strates1c Use ot DecrlPtion 

' ' fntel!Igenoe 

The strategic importance, to the Allies, or the 1ntell1~ 

senoe derived tro.m aeoryptions, concerning u-Boat operat1ons 1 is not readily expressible in figures. T.lle great magnitude 

ot the O\mtribution, 1n the strategic sense, of this ~orm. ~f 

intelligence? t~ the eventu~l v1otorr over the m.ost serioas 

tllreat of failure in this essential phase ot the war is 

1nd1cnted by noting the particular services it rendered. 

(a) Decryption illtelligeD.ce made 1 t possible to ob tai.o. 

a very accurate, complete 1 and fairly up-to-date p1otl.U'e ot 

the general c.b.araoter of t.b.e Germ.an submarine operations: tho 

areaa ot U-Boat infestation, the nwnber and 1Gent1ty of the 

boats o~erat1ng in the several areas, and their obJeot1ves--

wb.et.b.er coastal or trans-ooeanic co.nvoys, iqdependents, ad..ne .. laying, etoo; allot whioh were helpful in plal'llling antisubmarine measures, including c:>nvoy r:>uting aAd defense, and 

offensive operations agaizlst the U-Boatso 

Tw~ striking instances ot the application ot decryption intelligence in this reapeot are the following: 

(lJ In January 1943, the Allies tirst began reading the 

German submarine raa!o trattie promptly and completely, end 

helloe baa accurate knowledge ot the current disposition·or the 

UmBoa t groups. As a oo.nse1.4uenoe, some of the UK•US c:>nv oys 

were, tor the first time, taken otf the standard r:>utest w1th 

the result that the U-Boats all•4e :>nly one o.:>ntact during the 

first tw:> weeks in ;ranu.aryo * 

* bOenitzt's remarks on this .,ooas1on are interesting. He writes 

in the BdU war Dier1 of 15 January: "Neither the 9 SC' nor the 

'BX' oonvo1 were o~ntaoted.o~probably ~so• and aBX• p~ssed to 

tbe nortl1 ot subma.rine disposition. These two c.mvo1s bring the total up to tour that have beell .missed sinoe 31.12" It must 

be asswaed that tb.e enemy has lett the o~nvoy routes that he has 

been sailing for nearly 6 months and is again scattering his o.ond 

voy routes. this development is a great drawback t~ attaoks bf 

our boats, but was only to be expected. As bas already been 

emphasized in this war Diary, it was qu1te inexplicable why tho 

English stuck so stubbornly ~., almost the same c~nvoy routes tor 

s1.x .months, wl11ch greatly s1.mgl1t1ed finding his o:>nvoys.,n The o.,nv»1 routes in the North Atlantic remain.eel "SOe. tteredtt 

throughout t!le remai.nder ot the period ot the U-Boat .menaceo 

4-1 

TOP ~S-£CRET~-
m smnr -•MJ?FJ9r St t:if t ., 11.0> .a21i-s2 SECURIT\' INFBm,~-~ (2) on 24 'M81 194), BdU ordered nearly all hie boats to 

leave the North Atlantic, and on 26 Ma1 designated 17 ot them 

to torai a gatrol line some 7SO miles s~uthweat ot the Azores by 

l June, in order to attack US-Gibraltar shipping. The 24 May order was deor1pted the tol~owiag day; the 26 M'BY message was 

read on 3 June. and cont1l'al.8d tl:le previous order. As a result :1 

not onlJ were the bhreatened convo7s diverted with such success 

that not one ~ontaot was made through~ut JWJ.e, but the Allies 

were able to re-deploy the carrier escort groups that had beeA 

protecting North Atlantic o~nvo1s

1 and these carrier escorts 

carried out a tllree-.manth 11 s oampa SA ot highly su.ccesstul h\1l'lterk1ller operations against tl:Le u-soats in the mJ.d-Atlantic. This 

'campaign is discussed 1n Seo~lon 4a3w 

(b) Decr1ption Intelligence provided detailed, aocu.rate 

information: of tactics em.ployed by the U-Boats, h8noe making it WUleoessary in some cases ta learn them ill the oostly sohool ot e~perienoe. 

( o) Deoryptlol'l Intelligence provided ~·.oourate and oomgrellensive int'orma tion on new weapo.ns and other devices, au.ch 

as searoh receivers. · 

(d) Decryption Intelligenoe provided an excellent cheok 

on intelligence trom other sources and supple.mented them. 

4.2.. :raot1oal use in the Defense ot Cony5JY!· 

With respect to its tactical value to the Allies. the 

decr1pted intelligence could be used 

(l) defens1v•l7, by diverting convoys alr$ady 

en.route when prompt decryption 9rovided 1Aformat1on on new concentrations ot u-Boats along their original r~ute; 

(2) otteneively, by using current 1.ntormat1on 

ot u-Boat ooncentrati~ns t~ veotor hunter-killer 

groups to the area. This will be discussed in Se~tion 4•J• * 

* De1'ene1 ve and ottensi ve uti-su.bmarine measures could some=. 

times be c~ncurrent; t.tiat is a c~nv~y .might be diverted because 

of special intelligence, while the escort oarrier group a~taoked the U-Boa t pa ok: • k'3e91llg the boa ts sub.merged and thus making 1 t 

very 41tt1cult for tbem to close the COD.V076 

4 ... 2 

T 0 P S E C R E T CANOE 
PF ~ cIJt:i: ~5t§5·'1., •' C ) 271 t:. L C I\:: :C LO 2 • ., a 

SECURITY INFORMATION 

The evaluation of the taot1oal etfect1ven.esa ot deorJPtion 

lntelligenoe to the Allies. 1n the defense ot cmivo1s is not at 

all as stra1gb.ttorwar4 a probiem ae is its opposite number, 

41sou.sae4 1:4 part ). In that oase, aa has been ab.own~ 'it is a 

fairl1 simple procedure to determine tbe particular convoys on 

whiob the Gersans had good X-B intelligence, and hence a direct, usable measure of ettectiveness ot this 1n.tell1genoe is 1.mmed1atelJ available. '1'111s .meaaire is not applicable to Allied 

lntelligencev · 

COllsider tAe t~ur possible cases that might arise in a 

U-Boa t; war against .oonvoys: 

CASE I: Ne1 ther side bas; 1ntell1ge.noe. This oond1t1011 did p.ot arise 4\&rillg a111 interval· ot lS days or more 1.n the geriod from 

l Jul7 1942 to 31 March 1944. 

· CASE II: The u-.aoat command has x-B intelligence o.n o~v~1s; 

tie XII1es are restriote4 to reoOAl181ssanoe. Tnis was the case 

du.ring Period I, trom Juli 1942 to December 194~. The result 

slloula be to 1noreaae the nwnber ot oontaots sinoe .bJ.a intelligenoe would'enable BdU to concentrate his boats in the known 

areas o t greatest convor c1e.us1ty. It waa seen in part l ot this 

report that the oo.utaot rate was greatest dl.ll'!Jlg tll1s period .. .. CASE Ill: The Allies have accurate 1ntormat1o.a. on u-Boat dis9oa!tlods and movements, while the enea11 1a dependent· OA U-Boat 

reoo.ana1.asa.rice. Tb.is was the stete of affairs aurins Period IV 

(Segtember 1943-Maroh 1944), and t~ a lesser &%tent ~n Period III 

(l Jwie-16 septe.mber 1943). This 1.llformat1011 would ell&ble tlle 

Allies to route oonvoys around lmowa u-Boat oODoentrat1ons! or 

to divert theJn enro~te; thi~ should produce ~ decrease in ~he 

p.robab111t1 ot a OOAVoy bei.og contacted •. As a •tter ot tact, 

the contact rate dur1ns Period .IV was less than two-thirds of 

that in Period Iv (During Period III there were no operations against North Atlantic oonvoys.) 

CASE IV: Both sides have partial 1.atelligenoe of each other• s 

move.manta. This was the usual state ~t attairs throughout nearly tbe whole Period II, fr;)JJL January 1943 to May 1943. 1.11 this case 

the OQntact rate might measure the etteot ot tb.e x-B intellige.a.oe ot 0::>11vo1 .movements, b1.1t 1a .not clear that 1 t would 

measure the etteotiveness ot Allied intelligence; that is t~ say, 1t ls not a priori evident tl1at tbe existence af Allied 1ntel~1-

genoe woula atfeot the nwnber ot oontaots made by the u-Boatso 

In general Allied 1ntell1ge.noe restricted t~ u-Boats near 

·enough to Litercept 00.DVOJS O.il WJ:l10h. they had 8004 1.a.tell1ge.noe, wollld ·aot atteot; the contact rate, because the greater mobility 

ot the u-Boa t woulc1 tend t~ .neu.tral1ze diversions. Allied 

"4-3 

T 0 P S E C R E T CANO~ 
F WtA9;!6,§0 ,, !SP SBQS!' r ~ .c ~ .l\.. E (L()) 2.a11-;2 

SECURITY INFORMATION 

intelligence ot.U-Boate near oonvo1s on wbioh the ene.1U1 did not 

bave good intelligence, should 4eorease the number of oontac"'!'i:" 

ActuallJ, of course, tbe sitW1tion, as regards intelligence, in 

the Atlantic o:>.nvoy war was not as simp~e as this, and was co.m.-

pl1oate4 by other factors, auoh as weat.b.er, U-Boat oapab111ties, etcc However, it seems likely that, on the average, the character and extent of tb.e 1ntell1genoe or··u .. Doat moveiu.ents ,Possessed 

bJ the Allies migbt, 111 any given time interval ot signitioent duration, be retleotea in tbe c~ntaot rate. 

several approaches to ttle problem suggest themselves, and 

caa. be torA'IUlated ee follows: . 

(a) How did the overall quantity of pertinent deoryptione-- for example, the type nun measages--duri116 8111 given interval 

attect the oontaot rate? · 

(b) lfOW did the knowledge ot particular U-Soat wolf ... 9acks, 

obtained tr~m aeoryptions, affect the ability ot these groups 

to contact convoys? 

(0) What tracti~n of the non°contaoted convoys owed their 

1.mmwlity to tactical a1versions ordered because of knowledge ot 

1.mminent U-Boat menace, wlum such knowledge wa~ attributed to 

decr1ption intelligence? 

The findings on tb.ese three "u.est1on.s are as follows: 

(a) Bow did the overall qwantity of pertinent deorypt1one--

tor example, the tYPe "111' messages--d11r1ng any given int~rval attect the contact rate? . 

IA Table X the contact ooeft1o1e.nts are listed by months 

together with the number ot t7pe "111' messages deorrpted within 

) cta1s ot t.ranamiss1on8 beginning with uaroh 19430 The .ltlOnths 

tro.m. Jul.J to Deoember are sign1f1oant tor comparison because 

during this period the Allie• did no deor1pbingo 

'!&P WRJR T 0 p s E4ft; RE T.MNOE 
SECURITY 1NFORM.~T10;\l TABLB x 

Oo.ntao.t CoettioleAt , • I RSK'-OblQftl11on th overall ad.sect convoys 

J'117 1942 

AUguet 

septe'®er 

ootober 

November 

December 

Average tor period I 

;ranuary 1943 

:rebruary 

March 

April 

May 

' Average tor Period II 

Se,Pteaiber 1943 

October 

November 

December 

Janua.ry 1944 

February 

Marob. 

Average tor Period IV 

1450 

){)SO 

2100 

20;0 

4550 

2400 

-

26SO 

I 2300 

1950 

1700 

2600 

1900 -

20;0 

23SO 

1150 

1550 

650 

22SO 

3500 

sso 

-

l?OO 

4-5 

0 

2900 

1850 

2000 

5100 

2l~O 

24;0 

600 

1750 

)l.SO 

1600 

2450 -

1400 

:t3SO 

0 

lSSO 

700 

2.!SO 

3200 

sso 

-

1700 

T 0 P S E C R E T CANOE 

NU.mber of 

TJpe "1111 

Deor,gted 

Within 

) l!l,S 

34 

60 

60 

2.t 

80 

28 

43 

4S 

31 

33 
I : 

SECURIT\i' INFORMATION 

There is no direct correlation between the contact rate 

and tbe volume of promptly decrypted communicattone of the ttM" 

type.. This 1 s to be expected, ainoe the nwnbe:t or such messages 

transmitted by BdU fluctuated widel.1, 8114 depende~ on tlle state 

of German x-B and on the num.ber .:>t c~ntaots itself (there were 

likely to be more messages it few c~ntacts were made, lees it 

good intelligence was scarce). 

It is apparent tllat the great value ot decryption intelligence in the defense or 00!1V.:>7e cauot be expressed quantitatively by this measure. 

( b) :tro" did the .lcnowledge ot gartlou.lar U•B:.&t woltpaclc:s;f obtained tr0D1 decrypt1ons, atteot the abill tr 

of these groups t~ contact OOllVOJS? 

Tha manner in wnicll decryption 1ntelligenoe played a part in the wolf-pack operations has been described 14 the Intr64uotion and Part 1.. From l March 1943 t:> )1 March 1944 th.ere were 

34 pat~ol groups (as distinct tram attaok grou~s formed attar a 

convoy had been contacted) in the North Atlan tio. The following 

Table ll sWll.lDllrizee the relation of the eontaot rate to the decryption intelligence possessed by the Allies. 

Relation between Oontaots and IAtelligEtDce ·on - -'iJ"..aSoa t t&roups 

Number of cases in whicn decryption 

grovided timely intelligeaoe - - - - - - 20f= 

Number or contacts made in these oases -·~ - - 16 

NUmber of cases in wb.icb deor'J'p t1ons came 

arter the contact or not at all ~ - - - - - 17* 

Nllmber or contacts made in these cases - - - - 15 

No conclusion can be drawn. from these figures, except the 

conclusion that this approach does not field a q~antitative 

measure of the value ot Allied decryption intelligence. It 

must be borne in Dlind that t.b.ey do not take into oansideration 

some or the :factors that affect tb.e contact ratei tor exa.m.,ple. 

they do not in.elude the tao t the t in some oases a 41 version 

made, P"ssibly, as the result ot timely decryption, kept e lc.=~se pack of boats uselessly sweeping a certain area, while 

IJ!ffieappa:rant aisori,Pancy is due t~ the tact tbet a long-lived 

srouprr ''MEISE'' 9 was assigned consecutive gosi tiolis tor tbree 

different iJonvoys; another, "LEO'lhEN", tor twoo 

4-6 

T 0 P S E CR E T CANOE 
(LO) 2271-52 

SECURITY INFORMATION 

PDNC-NSS-)46 

other possible targets skirted st1f.ely around the danger area; 

nor that in some cases, even ·when contact was eventually made, 

it had been delayed by diversions to a point such that BdU 

called ott operations very soon after contact because too long 

a chase was involved. 

(c) What traction of the non-oontaoted convoys owed 

t.b.eir immunit~ t~ tactical diversions ordered 

because ot kllowledge ot imminent u-Boat menace, when sucA JcnowledGe was attributed t3 decryption intelligence? 

It has not been possible to find the answer to this question, 

tor the following reasons: 

( l) It is not possible to determine bow many di versions 

were executed as a direct result ot th.e menace ot near-by submarines, as ~sti.o..ot :trom. di versions ordered because or weather 

and ioe conditions, or as a kind of routine device to contuse 

the u~Boat command generally~ Dtlring the period from l December 

1942 to 31 Mey 1943, every UK-US c~nvoy, save one, was diverted 

frolil. 1 ts original route at least o~oe, and most ot the convoys several times. ·'In the case of ab~ut one-fitth of these diversionsi the evidence available in the C&R reports indicates quite clear y that they were due to the lcnown or assumed pro:x.imity of 

submarines; .. in the case of perhaps halt, it 1 s a reasonable . assum.pt!on. In no case has it been 9ossible to attribute the 

intoxmation ooncer~ing the presenoe of th~ submarines directly 

to decryption intelligence, as distinct trom D/F and air reoonnaissanceo 

(2) With ~egar4 to tho convoys that were not contacted, 

it has not be.-ll found possible, save in a veey tew isolated · oases, to state a det1Dite reason tor the failure to oontacto It 

might be due to a tactical divers1on9 but also to the weather oondit1ons9 to the taot that B4U was concentrat1ng the U•Boats on 

certain oonvo1s about which he had very good X-B 1ntell1geD.oe 

or to the tact that .most ot the boats were o!lasing oonvo1s a1! 

ready contacted and th.Qs were not available tor searoh9 

4o)o Ottensive Use bJ the Allies ot 

-= iiiorypti2n ihtellif?Jn!! 

As has been m.entione4 (Section 4ol), intelligence on u-Boat 

movements obtained bJ the Allies tro.m decrypted messages in Ma.7 

TOP S !i.,C R E T tANPE 
'f0P BBSRB'f (LO) 2271-52 

SECURITY INFORMATiu1·:, 

and June 1943. was iristrwnental in inaugurating the highly successful ottensi ve campaign against the German sub.marines i n 

the swma.er of that year. The functioning o t decryption intelligence in this campaign is discussed as a representative example of t.b.e offensive possibilities of this kind of intelligenoe 

(Seotlon 4.)ol.), In addition, the part playe4 by decryption 

intelligence J.n. the c!estruot1on ot the German fleet of retu.eller 

sub.marines 1s considered in Section 4.)02. 

4., .1.. Bunter-Killer O eratio.ns ainst the U-Boa ts in the Mid-

"'- an c une-Augus • n i ~a1 1943 BdU oroered most of 

"filie lort! Ktli\ntio - oa s t~ the vicinity of 350N, 4a0W, about 

750 miles southwest of the Azores, to 1ntereept a us-Gibraltar 

convoy on or about 1 J12ne. This message was decrypted within a 

day by the J!.l.lies1 thus nullifying tbe expected advantAges or 

the supposedly surprise move. A seoond message, transmitted by 

BdU on 26 May, organizing the boats into a pack with a designated patrol area, was decrypted on 7 June, and thus oonfirmed the 

shift ot emphasis t:> tb.e Mid .... n.tlantico Thr;>ugh:>ut the summer, 

Allied deoryptions, although scanty and frequently delayed (see Section 2;2 end Annex 2.2) c~tinued t~ supply 1ntor.mat1on 

regarding U-Boat movements t:> the Allied commands, wh1oh in 

several cases made it possible to vector CV!: groups to their 

prey instead of having them syste.matically search a large area, 

thus effecting~ very sig.n!tioant economy in toroe requirements~ 

(a) :£!!e +ttaoke on u~Boats bl.9VE.groupsu 

All the attacks by· CVE groups occurred in . the area 

bounded by 2s0 =450North Latitude, 20°~soc>west 

Longitude. In tbis area eocordiilg to the OOMINCH 

listing, Allied AfS forces carried out during the 

period trom 1 June to 15 September 44 attacks in 

which there was suttioient evidenoe ot the presence 

ot a submarine (A ... G Assesam.en ts) o Of these P. lj 

resulted in sinking and 9 damaging, U-Boa ts; 1ille 

remaining 20 were assessed either as 1'no damage" or 

es •1nsuf'ticient evidence of damage.~' 

Ot the 44 attacks, ;5 can be identified as having been made on )0 known u .... Boa ts. For details of the 

attacks on individual boats, the reader is referred 

to Annex 4.), which lists all the u-... aoa ts that 9 according to the daily listings in the BdU war 

Diary, spent .more then two aays in the area. 

TOP S E C R E T .CANOE 
REF ID:A65650 '.f/' tor1 SECRE 

'110:1:' BE.ORB! 

SECURITY INFORMATION 

(LO} 2271-52 

"lll\'C-•SS-346 

All b~t 7 of the 44 attacks ooc~rred in nine campaigns; and six ot the seven exoeptiOBs reoel~ea F and G assessments. The nine oe.m.paigns are 

swnm.ar1ze4 in Table XII. 

TOP S E C R E T .. CANOE 

4 .... 9 
01 

&D 

ii 

,... 

~ 

~ 

CM 

-

s 

-

REF ID:A65650 

--.-..-"'l---~~--.-..~..-.~------~,.-,~··:"':""_"'·--*------------·-·---·----·c-·b-a-r--ae'-.--ar--~·~~---All~~,--_..~D··-~-c·Tr.7-·--.;P~_...ion..---.._...._ nR.w <NE J>Ostti'iin Results wg VA -1.f'Pu .., .,, '" 

G:roue 

l. 4 .... 6 BOOUE JOOBc 4)0N 

June 

1943 

2o 7 .. 12 BWJE 310?4., 34<1df o 

c1ane 

Jo lJ&->16 · CORE 270M.,)4oWc 

Jul¥ 

4o l41Pl5 SANTEE 340n ci" 2"°'" 1 fie 

JUL.y ; . 

5,. 23 Jul;;-- BOGUK 35°§ ,, 26°''" c 

~- - -··· .. 

60 29 July _ SAllft'.rlC~ _ J;°t-1 ' 35'.'\1., - - 1. 7-ll CARD 39°M ~ ,3So1l" 

AU&c 

-.... 4/01 Attacked Tall~ .paek, 

sank U-21.7, damaged U.....226i 

At.tacked 3 othera_, 

7/6:DStSged iJ .... 753 

12/6: sank u ... us 

{RGtl\eller) 

San~ tJ-487 -(Refueller-) am 

u-6•t, damaged another,, 

attacked a f mrth.: 

San.toe U ·.J.60 and U-509 e 

attacked thre~ ot.harsa 

&mk u-527 and u-613, 

damaged U-373 o 

SsrJt \J ... '43 

Sanlt U-ll 7 (.Refueller),, 

U-664.11 U-52S .. Attacked 

U..-66 four tiaoa after 

dMag:U1g he- -on .3 AUS~· 

Dama.gad u-262 ~ 

I - 0 _Intollksce -.-

Excellent<) 'Ibo l June locnts.on ot tbe 

pack known b;r 2S 137" A 26 Mq 

message, read on 7 Juno, oont.i.rmed 

formation of !)t'.Ok TRU'l'Z and gave 

patrol are&o 

Very Good. U-460 e.nd U-lJ.8 aent to 

bGlp U..,7S81 on 8 JUM.. This 

DJasage deCJ'fpted on U Jums .. 

• 

ione > From. 30 June ti.> 12 ,Tul.7 aU do• 

crypUcns 4S da¥a or mori11 late'· Frail 

lJ-16 July' all at least 2 nek:c lato9 

except reports ct attacko 

Kono,, Sea V..lldsr a .. 

iomt .. Sam& ae under 2" t='rCB J.7 Jul;r 

to 2) Ju.13' all moaeagea 2 wcska o.rmore lato., 

Mono.. om meaas.p sent b7 U*4~ on 

20 Jul7 waa decl"J'pted on 29 J\Jlf:. 

Good" U-117, u""66, and U-664 nrG 

ordored to a rond~zvoue on 30-31 

July; museagea dec:rypt.ed DJ 

l AUgu6t:. 

0 

r;=i 

J 
CVE 

• • Groug 

9 co 2"/ A11..g. CARD 

... ·~· . . . 

REF ID:A65650 

TABLE XII(continued) 

PoaiUon 

·.· 

.. ' 

• •• 

Suk u-lB.S, a u...a4_ 

daD!l.Pd u-406J 

Slltk U--84'1 (JletQeller) .• 

Attacked u-soe .. 

Character ot Allied Decrn>tion 

IntelligenOii 

Ver7 Good? From l!i • 20 Auguet, 

neal'l.1' 20 pertinent meaeagea dec17pte 

wif'Al 4 dqa or lea• lase A 19 Auguet 

meoeaga ord.oring U-84'> t9 i-etul mne 

U-Boata (incl" U-185) a\ poaitim 

ot att.ack wao cisarypted on ~ ~ug ... 

Botb CORE and CAim operated 1111rq 

e1nmltamouel.7 iTI the IUil a1roa., 

V•'l!J' Ooodo SH 8-:. 

"' .. 

'J 

~ I 

u 

r 

If 
, 

(LO) 2271-S 2 

SECURITY INFORMATIO~l A signi:f'icant characteristic of all the attacks listed in 

Table XII is that they involved ooncentrations of U-Boats, most 

of these refuelling rendezvous; in only one ot them-·the SAN'.fE.'E 

attack of 29 July--was the bag only one boat. This tact 

indicates excellent intelligence. 

It is evident trom the o.b.r~niole ot these OVE Hunter-Killer 

operations of the su.mm.er ot 1943 th.at decryption intelligence 

was of tremendous potential aid t.:> the Allied command. In the 

caae ot five ot the nine etiaoka described in Table x:a:i 4eor,g\ed 

messages could have been usea directly to vector the uv~•s to 

the U-Boa t .Positions., Wi tb. respect to the remailling tour attacks--

those in July--whe.n no hel.ptul decrypted messages were available, 

decr9ption intell1gellce was indirectly responsible t~ a greet 

extent tor the eftectivenese of Allied intelligence in th.at 

(1) decryption intelligence had. during the previous months, enabled the Allied c~mmand to understand the pattarn 

ot the German retuelling operations; conse~uen~lJ, 

(11} in the absence of actually decrypted messages desigllating a specific refuelling rendezvous, any unusual 

amount of racJ!o traffic originating 1n a relatively small 

area and picked up by D/F could be evaluated intelligently with re~pect t~ the probability or its indicating a 

rendezvou.s; 

(iii) U·=Boats could be distinbllished by .m.sa.ns ot RFJ? 

and TINA; but decryption intelligence definitely identified 

a given u-Boat as a refueller. Hence a message sent by a 

boat identified fr~ previous decryptions as bei~g a refueller, even if it could not be decrypted, might reveal the 

possibility ot a refuelling ren.dezvouso 

There is a possibility that tlle decryption service supplied good information that was not exploited by the Allied command, 

either because forces were not available, or in order to avoid 

danger of 001119r~ising t11is source.. lt is true that in the spring of the .year several refuelling rendezvous were discovered promptly from deorypt1ons, without the Allies using the information actively> during the summer, however, the evidence of the decrypted .messages 

1nd1ca tes that all tb.e available pertinent infor.mat:l.on was 1'ull:; 

exploited" 

In passing, 1 t should 'be stated that the performance of the 

Allied Hunter-Killer groups during July and August of 194), aided 

TOP S E C R E. T GANO! 4•12 
SEef1nJfY'.1NfoRMATION (LO) 2271-5 2 

by deoryption intelligac.oe, appears all the more remarkable and 

brilliant, 11vt1en 1 t 1 s realized that during these 60 days, nearly 40 attao!cs, resulting 1n 13 U-Boats sunk and 5 others damaged, occurred in an area extending 1200 miles by lBOO .miles, in which 

the average number ot U-Boats at any tilne was only 14. In tact, 

during the latter gart ot July, when the July attacks occurred. 

the average was 10. 

{b) The Etteot ot Allied necry~tion Intelliience on ~ne Probabil!\f-or a tr-Soa ·se!iys Xtt!c ep. 

The effectiveness of Allied decryption intelligence in the 

offensive operations just describec oan be expressed quantita- tively by the increase in the probability Of a U~Boat being 

attaolced as a resul.t of its movements being discovered from deo~ypted messages. It is assumed tllat if the position ot a 

boa' ls revealed, 1 t bee::>tlles more th.Eln normally vulnerable tor 

a certain interval as a c~nsequenceo (In the oaloula.tion given here, this inte1-val was assumed t~ te 5 days; the validity or 

this assumption is discussed bslu~o) If the co.mm.u.nication ~ batraying the position, either current or prospectiv~, is 

daoeypted t days before t.he period of e:x.tra vu.l.nerab1li ty 

up:tres. tlie boat is considered to be "in peril" during these 

! days .. 

P'>NC-NSS-)46 

Tlu'ee probabilities are compared: 

(1) The overall average probability of a U•Boat being attacked per day of its stay in tLe area selected during the 

period considered. ~his is given by the quotient of the total 

number ot attacks duri.ns the period in the area divided by the 

total nWD.ber ot U-Boat dayso 

(2) The average probability of attbCk per day to be 

expected by a U-·Boa t imperilled as a consequ.eJloe ot decryption intelligence. This is tha ~uotient of the number ot attacks on 

these u-Boats during the period while they were in peril, divided 

by the total number of u~Boat days in perilG 

(3) The average probability of attack per day expected by 

a U=Eoat not imperilled because of decryption 1ntelligenoeo This is tlie'"'~uotient ot the number of attacks on these b~ats 

divided by the total nwnber of days these boats spent in the 

e.reao 

The data required tor the oaloule.tiona are tabulatad in 

Table l ot ADD.ex 4o) 9 which lists 9 tor all u-.soats tbAt spent - three or more da7s in the area during the pGriod 1 June o 

TOP SECRETcANOE 

4-l) 
2271 .... 52 

SECURITY INFORMATION 

15 September 1943: 

{i) The decrypted messages pertaining to each boat, with 

date ot position or rendezvous, ana delay in deor1pt:t.on• 

(· .. ii) The num.be.r ot days "in peril" as a oqnseque.noe ot 

each dearypted co.mmnnication; 

( iii. ) at taok: s on ea oh boat during the days. 1 t was ~ 11'1 peri.1 0 •. 

The anal7sis yields the following reslllts: 

Total number of u~Boet Days in Area ••••••••••••• ~ 1919 

Total Nu.'llk>er of Attacks ••••••••••••••••••••••• ~-· 44 

Total Number ot U·=Boats Sunk ..................... "" lS 

Nwnber of days u~Boats were in peril.~········•o• 246 

NU&llbar or known attacks on U-Boats 1D peril,.~··· 9* 

Number ct imperilled U=Boats sunt •••••••••••• oGu• 5* 

Nwtber or u-aoat Daye u~Boats wel"S not in peril.o 167) 

Nu.m.ber of Attacks on u ..... Boats .no·t imperilled .. ~ .... ,, 'JS 

Number ot not~imperilled U-Boats sunk: ••• ~········ 10 

From these data we get: 

(1) Overall average .Pl'Obabi·lity ot attack 

per day in the area........................... 2o)" 

(2) Average probability ot attack of imperilled 

U=Boat per day in the area••••••·-·••••••••• ).7p 

()) Average.probability ot attack ot nonimparilled U-Boats per day in the area...... 2ol~ 

*Not i~aluding U-117, which was sunk one day after the jeopara1 interval expired. 

4-14 

TOP SECRETCANOE. 
!6P ffil>RB'f (LO) 2271-52 

SECURITY INFORMATION 

"R•C-NSS-3•6 

It appears that the average chance of attack per day to 

be expected by a U-Boat assumed to be in extra jeopardy it his 

position was discovered by decryption within S. days was nearly twice as great as that to be expected by boats ot which this was 

not the caSeo 

A similar, more pronounced trend.is noted in t.b.e compara- tive averase probabilities per day of being sunk: 

( l) overall average probability of being sunk 

per day 1n the area........................... Oo8~ 

( 2 J Average ,prob abi 11 ty of 1mper.l. lle4 u ... Boa t 

being sWllt per day in the area ••••••••••••••• & 2o°" 

(3) Average probability of non=1mper1lled u-Boat 

being sunk per day in the area................ Oo6~ 

The choice of five days as the ~•extra-jeopardy" interval 

is only to a certain extent arbitrary. A lO~day interval 

places ~st ot the boa ts in jeopardy, and includes a large traction ot the total .ttumber of u-Boat days and nearly ell 

the identified attacks. A 3-4 day ,interval results in a triv= 

ial case because ot the extremely small number ot deorypt1Qns made within that time during this period and because practi~ 

call.y no attacks would be included. A 6-day interval. gives · probabilities oompar~ble with those foWJ.d by using a S~day 

interval~ Tne~e considerations make it reasonable to conclude 

(a) -tb.at the 83SWllpt1on Of 5-6 d87S as the nextra joopardyn interval is valid; and (b} that the direct tactical value ot 

decryption intelligelloe in ottensive operations dropped sharply if decryption was delaJed .more than S-6 dayso 

1.,..3.20 Allied Decryation Intelli§enCe in Relation to the 

DEisGruotion of the Ger.man Refueliing-,Xeeto 

Unless they could refuel while on station~ the small 

500-ton T7pe VII and 7SO~ton Type IX U-Boats were restricted 

to opera ting wi thill. S00-600 .miles tro.ra their bases. The Germ.an 

command first used surface ships for suppl7ing the boats, but 

this became impracticable 1n view ot the increasing Allied supe~iority in surface ships and VLR aircraft, and the Germ.ans 

were forced t~ build submersible supply boats. i'wo types were 

designed: 

i'6P SEORB'f 

TOP s E c R E T CANOE -15 
(LO) 227J. .... )2 

SECURITY INFORMATION _ ( 1) TJPS X B, a cor&.>~.nc~ i1'!inel.a7er and supplly boat, w1 th 

a fuel capacity of about 426 cubic meters, and 

equipped with ti"IC torpedo tubes: 

(2) 'l''fP& XIV, for 1uppl7 purposeu onl7, w1 th a tuel capa- cit7 or about 740 cubic meters; no mines were carr1ed9 and the7 had no torpedo tubes. 

I 

ThA first refuellers~ one or each type, we~e put in ~peratlon in April 1942. The Ge!'DJ8.ns pushe4 oonstructton ot these vit~~ craft with such energy that a- rear later thft)" had nine 1D 

ope:ration, besides having lost t10 • Up to the end of the war 

they.commissioned 18 refuellers (10 type XIV, and a fype X B)o 

or these 18, 16 were sunk, nll b7 June 1944. 

The loss to the Gel"mane or a retaeller was extremsl7 pa1n- rul w !t moant not merely that a ve'l!'I valuable, hard-to-replace craft was lost; but-it also involved the shattering·ot ce~~r~lly 

prepared refuelling schedules: ttnd the Cl)JlSequent ::Si:lrtlption Of 

equ.all7 ca:re!'ull7 prepa~cd ope?·a.tions progra?:lS azni!lst convoys c 

This was especially tne case if the refueller· was s\Ulk Wh.lle on ~tat~.on 1.n m~.d-01HJ•an.. :rt w~e among tbe l~ttal." th!\t the CVE tamk 

gFoups took t..""leir heavy toll, and it was in this task, as shown 

in Section 4 .,3,.1~ that decrypti ora 1.ntal11. gence wee of e ueh 

dee is i ve po·(.€.£?.~ ial impo?·'. i.;;u-:iet;;:..., , ~ t I • 

A l:ts t. · ~,r s.1. l. the H·3i.'m.an~ reftl&ll-s::::•s ~ w 1th data concerning sinkings sna the contribu~~ion_· C"Ji" decz•ypf..;lon inte:tl!gence 1n 

each CcUHlli' i~~ ;>resented_" l::l '!1!1,blt.JJ, r:r of Anne,~ 4oS.> Following is 

a sumrr.a1•y chc-oniole of fus :r-·ari..~ ellers ·.) Of th® 15 ret'uellera 

sunk, ·· 

{ s) S5..x were sunk i~'l t.rnna it to (or fromj thoir stations" 

five or "thees in th~ Bay or Biscaro In these coses there was~ 

of course~ no decryption i:ntelligenoe, since the boats were not 

men·tioned over the ai::r un·til they a:rrivad at the ii- stations o 

(b) or pie ten sunk on station~ 

(!) two were sunk in 1942• before the Allies were 

dec"."Pt1ng; 

(11) in the case or three there 1s no evidence that dec~ypt1on intelligence was or direct aid in 

locatir.g _the;:.; 

PQNC-NSS-346 IP .BP B!SST TOP S EiC R E ,..{CANOc-· 
(L0)22'1lu52 

SECURITY INFORMATION 

~NC-NSS-)46 

{111) in the case Qf the rensa1n1ng t1ve. decrJPt1on 

intelliBence was so prompt and complete, ·as to be 

a potential direct means or locating the boats.o 

T•o of thesa·ca~es (U•ll7 and U-118) havo been 

discussed in the preceding Seotion 4o3&14 One mo~e was sunk in"Octobe~ l94S• two days at~er 

transmitting a rendezvous position which was 

decrypted a few hours later·; & fourth in April 1944• four days artar t~ansm1tt1ng a rendezvous 

dec?'l'Pted · the sam.$ day; and the .fi.tth in June 

1944. en the day·efter·she betrayed her position 

in a message Which was decr-n>ted within a raw 

hoUX'S a 

T 0 P .a.,E C R E TtANOE 
(L0)2271 .... 52 

The findillgs ot the study ot the effectiveness of deoryp- tion intelligence iJ1 the oase ot botll sides 1n the Oonvor Bat .... tle of the 11..tlan t.1o are ewaawrized as tollowe 2 

)olo Value ot DeOl'JPtion Intelligence to the OernYlD.Bo 

(a) The Germans obtained operatlonall.J useful deorypt1on intelligence on roaglll.J' .balt ot all our 0_0J1vo1s troa Zulr 1942 

to M&J 1943. AS a result ot the change ot aode in June 194). useful. x-B 1ntell1genoe was obtained on onl7 4 out of 87 aonvo1s from September 1943 to March 19~o 

(b) ·FrOJD Jul7 1942 to ~ay 1943, there were nearl7 alwa1s sufticien~.convoy~-on whioh deorJption intelligence was avail· 

able to keep the U-Boats wt1ch had any degree of tactical mobil1 ty, well occupied. There is thererore no consistent relation 

between.tluotll8.t1ons in a.rnounl ot intelllgence available to the 

eneJD¥, and .his rate ot contacting or attacking convoyso 

(c) The ebove tacts must not be interpreted as indicating that the ava1leb111ty ot ~ood ra41o intelligence did not have 

a .marked erreot on tbe suooess ot U-Boat operationso The information obtained by X-B intelligenoe on speoitic convoys enabled tbe U-Boat oo.mmand to select certain ones tor pack operations, either igllor1ng others or leaving their detection 

to chance. As a result. tne ett&otivenees of the U•Boate in 

contacting auoh selected o~nvoys was increased to about 2i 

times the f 1gure when no X-B intelligence was availableo 

(d) Regarded from the opposite point of view, discovery of, and estimation or tb.e magnitude ot this etteot, has per- mitted us for the tirst time to determine the true capabilities 

ot world war II U-Boats, operated as the Germans operated, to 

find and attack targets ~itllout benefit ot decryption intelligence. This intor.mation is potentially of t4e greatest value 

as a base in determining torce ·reqμirelllellts for the fQture, and extrapolating to the magnitude ot f~ture threats b7 boats 

having the sa.m.e or different obaraoter1st1cs. · 

(a) u-Boate having .. no decryption intelligence were apc:- parently capable of searching approximately only 1750 square miles per da1 for NortAA.tlant1c oonvofso Their &fparcnt search 

rate when all c;>nv:>7s are iuoluded (even tb.ose wliose locations 

were ao.mpr'Oiiiised bJ decryption) was about 2350 square .miles 

per dayo Their ab111tr to find C!)lJlpro.u:daed CDnV~JS alone was 

significantly higher--1f it is expressed! purely conventionall78 

as a search rate corresponding to them. tis eq~1valent to 

28;0 square miles »er day; ind1Cut1ng an etfEctiveness per 

; ... 1 

TOP S.E CR ET .CANOE· 
REF 

•, .. -...... \··. "' .. ':,.~ • .!,\·.,~· 

~~lirle i/ 

"' ' .. 
7IQl' szem ;A{.:j ~F~~~}ls~-._ <1.012211-52 

SECU~lltJ~fb{J;R~~at as Cl1e u-soat opel'Btlns withOut 1a- ~ .tellige.noeo 'l'he abilitf of U•l)oats to find o:>.m.prom.1.eed ooa.vo1s 

spec1t1cally seleoted by tlle U•Boat oommand tor attaok was verr 

hish•-expressed as a searoh rate, 1t was equivalent to 4450 

di square miles per d&f m a 2SC>.' 1noreasa over the search rate OJUUJ. 

nOA-ooapromised o::>nvo7s. . 

(t) ~he figures o1te4 above include the ettecte ot All1e4 

4eor;ption of Ger.man u-.soat co.maiw11cbt1onso DU.ring tlle period from J~ly to J.)eoember 19421 the Allies had no deo.17ptlon 1ntel11genoe on UuBoats; during this per1o4 the U·Boat search rate, oo.m.puted on non-oompro.m1sed 00Avo1s, was,24;0 aqwire miles per day. Tn1s is the nearest approximation to the real operational sea.roh·rate provided b1 the data~ It corresponds rotigblJ to a 

sweep width ot abo&it 10 miles. ··· · 

( &) COJD.parisoa. ot abl.P sia.Jd,n.gs tro.m oompromlse4 and no.noomprom1sed North Atlantic convoys makes it appear tbat• during the period from July 1942 to March 1944, probabl.J about 100 tewer ships td.gtit have been sunk from these oonvo1s it the U•Boats 

had been de.nied ·the benefit ot decrypt10Jl intelllgea.oeo 

2o2 Valu.e of DecryptiOJl Intelligence to the .A.llie'o .. 

(a) With respect to 1ihe defensive u.ae ot deoryption intelligence bf tl1e Allies (to divert a.o4 route convoys in order to 

evade known conoentral1ons ot U•Boa~e) it is not possible to 

express statistioally t.be etteot ot suob intelligenoe on the 

ability ot convoys to avoid contact by the u-Boats. The overall figures 1nd1oate tllat d&iring the period·trom September 1943 

to uaroh 1944, when the Allies read the Ger.man oommunioations 

ou.rrenti,, tbe contact rate was reduced to two-thirds ot the 

oontaot rate du.ring the geriod tro.m July to Deoe.m.ber 19421 when 

the Allies were not reading the German Cipher. This figure does not describe tale val&ie ot Allied decryption oompletel1. 

'l'he relative s1nk1g rate (per U•Boat cla1 per oonvo7 4a1 1n the 

area) on the_o,lleYll'iild, during the Sep. 194)-va.rch 1944 pa r1od, fell lo about one-sixth the value or the tulJ~Deoember 1942 per- iod. A gart ot this oollapse ot the U-Boat ettort ~st 'be as~ 

cr1be4 to the availability of prom.pt 1ntell1genoe on U-Boat · 

_.movements; increased etteotiveness ot anti-submarine measl.lre's ~ 

and the failure ot the x-B servioe to provide intelligence on 

convoys to the u-Boats1 were resRonsible tor some ot 1t. It ls 

not pos~ible to deterau.ne how m.uoh oredit should be eacrlbed to 

each of these taotors. , 

. (b) The ottensive use ot deorygt1on intelligence in hunt1.ag down and killing U-Boate was studied tor the period l gWle to 

lS ~p teJJLber 1943, 111 tihe area l.Jing be tween 25."N · - 4; N aud 20°w - 50 Wo . 

s-2 

T Op S E C R E T '·CANOE 
.,......--------------:--- - -

We:P SMllE'? ~~~F. w~~~OE... (I.0)2271°~2 SECURITY INFORMM-f . ~ " t K ::-

Of nine .maJor attacks oarr1e4 out b7 OVE taslc groups, decrypted 1aessases oould .bave been used direotlf to vector the 

oVJi;•s to the U•Boat positions in the oase ot five; these attaoks 

resulted in l; U-Boats su.nk an4 9 more damased. 

on the bae1a of ase~pt1ons explained in the bod.J' of the. 

report, it is found that the average probability ot a u-,oat 

compromised bf Allied decr7pt1on being attaoked per daJ of its 

stay 1n the area was 3o7~ as oompared with 2.1~ per dar tor 

a boat not so- ooap~is~ct--nearJ.y a two-fola increase. · 

The oorrespon41.ng probabil1tJ per 481 or a U•Boat being sunk wae.2.G.f' as compare&\ with o.~-a three-told 1.norease. 

Deor1ption 1ntelligenoe was directl1 ot assistunce in 

the destr~ot1on ot the hishlf iaiportallt German.eubmariAe ret~el~ 

ling fleeta Ot ten of tllese refuellers sunk on station in midocean, deoryptions ot messages revealing their pos1tioA could 

·have been used 41reotl1 to tlnd them ill the oase or tivea .. In 

the oase ot three others, deol'J'ption 1ntell1genoe e14ed indirectly in providing general information concerning the retuelling pro0 

cedure used by the U-Boatso 

____..... ..... ,,,,, .......... . 

subm.i't ted by: 

O.E. BEHRENS 

Operations Evaluation Group 

Approved by: 

JACIN'l 0 S'l'J::l.NBARI1l' 

Director, Opera~ions Evaluation Group 

S•l 

T 0 P S E C R E T CANOE 
SECURITY INFORMAflU&t ANNBX 2:1. 

Table I ot AaAe:r. 2.1 presents a summar1 bJ .months of the 

percentage ot the BX, so, encl ON convo1a on wh1ch the Germans 

had good X~B intelligence. 

TABLE l 

Extent of Ger.man X-B IAte1111en~e 

· NO. ot Oon.\to7s on 

Month and No.of Oonvoye whioh X-B Provided 

Year in Area "Good" Intel~igence Percent 

Period I - l Jqll·ll Deoember,1942 

July 1942 18 7 391' 

August 1942 17 s 47~ September 1942 19 7 )7~ octooer 1942 16 2 13~ November 1942 14 6 43~ December 1942 16 7 44"/. 

Entire Period - - - - 37/, 

Period II - 1 Januari-21 uay 194i 

January 1943 16 10 6)" February 1943 11 s 45~ March 1943 15 14 

April 1943 17 11 l~~ May 1943 ;.ao 17 SS~ 

Entire Period 72/o 

Period IV - 16 se2te.mber 1943-31 March 1944 

16~;0 September 1943 9 O · Oi& 

October 1943 16 3 l~ 

November 1943 12 O °' Dece~ber 1943 lJ 1 8~ 

January 1944 l~ 0 ~~ 

Februar7 1944 12 0 O~ 

Marc.b. 1944 13 O 01' 

Entire Period• - - - - 5~ 

Ave.rage tor All !rbree periods- .; - - - )~ 

T 0 p s E c R E T CANoe·:: 
(a) 

( b) 

Pll'<C-NSS-,•6 

'l'.ABLE II 

Es ti.mate ot the qwil1. ty ot the x-B in telUgea.oe 1 s 

indicated by the letters ''G" and "N". "G" 1nd1ca tes 

the availability ot X-B 1ntor.mat1on on the given 

convoy wh10b is considered t~ have been potentially useful to BdU 1n d1apos1ns his u-Boa ts if he w1 eh ea 

to operate against 1 t. "N'" i.ndioa tes the t W1 th re ... spect t~ a given c~nvo7, he had either no lntelligence, or that the 1ntell1Senoe available was ot no direct 

use, bscause it came too late, or was too indefinite 

or scanty. The estimate 1A each case is m.ede according t~ the criterion detined in section 2.1 ot the 

re9ort. 

The remarks 1n column 3 are extracts trom the BdtJ 

war Diary. The nwnbers a£e designations apglied to specific o~nvoy8 1D tlle Diary, and are 1no1Qde4 

tor convenie.uoe in reterenoe. In eaoh case in 'Which 

BdU .mentions X•B 1ntelligenoe pertaining to a given oonvo1, this is indicated, together with the Qse he 

made of it, it any. 

2ol•2 

T 0 P S E C R E T CANO£ 
'feP SEeftfi • i' 0 ~F "I~:~~~~ ~ :tJ Cl ft L (LO) 2271-52 

·.r-011R1~i ~r.:i.J' ¥' INFORMATfor; TABLE n (1) 

oonvo~s betwe8l1 u.s.-oa.uada e.11d· u.K. ;:z~tt !94i3x !!' 1m 

16 Seitember l~ll,Maroh 1944. 

X·B 

Intel- BdU $1.o.k: ... 

gonvor lipnoe war DiarJ contact 1ga 

-· 

J\ll.J BX 196 N 

1942 

m 19? N 

BlX 198 G 

BX 199 N 

SC 89 N 

so 90 N· 

·SC 91 N 

SJ 92 G 

so 9) N 

ON 107 H 

ON 108 N 

ON 109 N 

ON 110 0 

ON lll m 

ON 112 G 

ON 113 G :No.. )7 23/? 

ON 114 G 

ON 115 G mo. 38 3/8 4 

2ol•) . 

T OP S E CR E T CANOE" 
• eiEF,...~:~~5P!~ I ~:Ctl\:L 

'£GP SJ£CRE1' (l..0)2271 ... ;2 

SECURITY INFORMATION TABLE II !~l 

X ... B 

In.tel= BdU Sinlc:-

Month convoy llgenoe \far I>ie.ry contaot lnss 

A.uguat BX 200 N 

l9i,.2 

HX 201 N 

BX 202 N 

BX 20) G 

SC 94 N No. 40 'J/8 11 

so 9S N No. 42. DOubt that 

1 t 1s convoy o l')/8 2 

SC 96 G 

so 97 G NOo 49 31/8 2 . 

ON 116 N No. )9. No attacko 4/8 

ON 117 N 

ON 118 N ,.. 

ON 119 N X-B 90s. tor 14/B on 

13/So contused with 

SC 9.5. 14/8 

ON 120 G 

ON 121 G 

ON 122 G No. 47 22/8 4 

ON 123 G 

ON 124 G 

2ol-4 

T 0 P S E CR E T c"ttoE·. 
-- ~ 

9f ~F ];D.:.,A~§-50 ~ 

- 0 t' ~:ht KE 

!Im:' SECltET (L0)227l-52 

~ECURlTY INF-ORMATION TABLE II (3! 

x~B 

Intel- BdU 

oontict 

81.Dlc:- Month convoy ligence war Dier.v inga - - Sep te.mber BX 204 H 

1942 ' BX 205 N 

HX 206 N NOo 52 13/9 

BX 207 G 

HX 208 G 

so 98 N 

so 99 N 

so 100 G Ro. S4o 23 U/Bts 

to attaoko 18/9 5 

SC 101 G 28/9 1 

so 102 G 

ON l2S N 

ON 126 N 

ON 127 N NOo 50 9/9 8 

ON 128 N 

ON 129 N NOo S)o poor weather. 11/9 

ON 130 N 

ON l)l N 24/9 l 

ON 1)2 G No. S6. Lost Contact. a6/9 1 

ON 1)) G 

2.1-5 

TOP SECRETCANOE·~ 
•r o FF S~1t5fe'.E\ '?eP BllEJRE (L0)2271-)2 

SECURIT\' INFORMATION-~ II (4) 

x~ ... B 

Intel .... B4U S1AkMonth 

-- COllVOl" llgeDO,! war Diaq oontaot 1!§8 

October HX 209 N 4/10 1 

1942 

BX 210 N 

BX 211 N 

HX 212 N JIO. 62 26/10 7 

so 103 N Sighted 9/lOo 9/10 1 

SC 104 N lfOo 59 12/10 8 

so lOS N 

SC 106 G 

ON 134 N 

ON 1)·5 N 

ON 136 N NOo 58 11/10 4 

ON 137 N NOo 60 16/10 2 

ON 1)8 N 

ON 139 G NOo 61 22/10 

ON 140 N 

ON 141 N 

2ol-6 PflllC-NSS-'U T 0 P S E C R E T CANOE 
~ 8 ~F c.19,; ¥iS,Ej5~~ ;:, :n c n: 

'll>P Sl!IS R!i'i' (L0)2271-52 

SEeURIT'l \NFORMATION' TABLE II J 5 l 

J:-B 

1ntel- BdU Sinkuonth 

......,..._ oonvo1 ligence wa:r ])1arJ contact 1nga 

irovemb er 

1942 BX 213 N NOo 640 contused 

with so 107D 30/10 

BX 214 G 

HX 215 G 

BX Zl6 N 26/11 1 

so 107 G NOo 64., :•B: 

places pack. l/ll 16 

so 108 -G 

SC 109 G prob. !lOo 670 18/11 1 

SC 110 N 26/11 1 

ON 142 N so. 65a (contused with ON 143) 7/11 2 

ON 14) N 

ON 144 G NOo 66 16/ll 5 

ON 14S N u-518.attacks a c/v 

1J1 this v1o1n1t7. 21/11 1 

ON 146 N )/12 1 

ON 147 N 

nee ember 

1942 BX 217 N NOo 680 contu.sed 

with so lll nearb70 6/12 3 (SO 111 lost no ships)o 

BX 218 G NOo 690 X•B COl1ft58o 1)/12 

BX 219 N 

BJ: 220 N 

PRNC-NSS-)46 T O P a.s E C R E T CANOE 

!0P SEeRZf 
9p e ~F .J;Dr.A~~~ r ~:n~.n. 

'mP Sl!l9Df (L0)227l•S2 

~EClJRITY INFORMATION TABLB II (6) 

X-B 

IA tel- B4U staleMOD.th convo1 ligenoe war Diarr contact 1o.p 

neoeaber SC lll H 

1942 

( ota.) so 112 G 

so 113 N 

so 114 !l 

ON 148 0 7/12 1 

ON 149 N 

ON lSO c 

ON' lSl 0 

ON 152 G Bo. 69. (contused 

with BX 218)0 16/12 2 

ON 1,3 N NO• 70 15/12 6 

ON 1S4 G NOo 72 26/12 1) 

ON l'S I' 

JBD.U&l'J BX 221 G 

194) 

BX 222 G JC•~: p08o to place paCk:o 17/l 1 

BX 223 G X•B: pos. to place pack. 25/1 1 

BX 224 N N'Oo 4 1/2 3 

SC 11) G 10/l 2 

SC 116 G 

SC 117 G No. 3 23/l 

SC 118 G Hoo 6. X·B: pos. to place paoJc. 4/2 12 

PRNC-•SS-J'6 

TOP 81:8 CR E T 1

CANOE 

!SP BmRB'f 
(L0)227l-52 

J:coB 

Intel- Bc1U Sink· 

MO.nth oonvoz 11genoe war Dlaq oontaot 1.ne. OW» 

Januarr ON 156 G 29i12 

1943 

(otdo) ON lS? G 

ON 158 G 

ON 159 N 

ON 160 N 

ON 161 .N 

ON 162 .N 

ON 16) N 

Februa17 BX 22.S lf 

194) BX 226 G X•B poso to plaoe ,paok. 

BX 227 G Hoo 1). X-B ,PO&. to 

place paoka 27/2 l 

so 119 G 

SC 120 N 

ON 164 N 

ON 16, N NOo 9 17/2 ) 

ON 166 N ?loo 10 20/2 lS 

ON 167 N N'Oo 11 18/2 2 

ON 168 G Boo 130 ooiiruae4 

with BX 227. 1/3 1 

ON 169 G X-B to place paoko No m.eJlti~n ot slnking.7/3 1 

2.1-9 

PRNC-•.a>i> SEQRB'! TOP S E C R E T eANOE 
9j; g ~F c;lq.;¥\SJ>.5~~ o:ettt 

(l..0)2271-52 

·TABLE II (SJ 

X-B 

Intel .... BdU Sink~ 

1I\'.:l tj], ":"'.!'""l=:..lo-.=:--=--, oonvoz ligcce war Dia17 contaot inp 

~-i--.: ~~oh HX 228 G Noo 16. X-B to }':;J~~J plaoe gacko 10/) 7 

BX 229 G No. 19. X·B gives d1vers1ono 15/3 13 

BX 229A G 

RX 2)0 G No. 21 29/) 1 

so 121 G No. 1). X-B to 

place packo 6/) 14 

SC 122 G X-B pos. combined 

ops with BX 2290 · l';/) 9 

SC 123 G X-B posa 

,PBCko 

to plaoe 

SC 124 G 

ON 170 G oontaot not developed. l'J/) 

ON 171 G 

OM 172 G 

ON 173 G 

ON 174 N No. 20 26/3 

ON l75 G 

ONS 1 G X·B to place paoko 

IC" ... -::s:"'.=:t:.:o 

q • 1 HX 2)1 G Noa 24 4/4 6 .fapl":... 

J.91)-3 

::ax 232 G No. 26 10/4 4 

RX 233 G :No. 27 15/4 l 

2.1 .. 10 

PRNC-NSS-,06 

:eep SBGR:iT TOP 8 E C R E T CANOE 
9f · e ~F ~L\Jft:C 

i:J:Q:; ¥SAS~~~ ~)I' S!Cmt'l' (L0)227l..,52 

SECURITY INF8RMA.TION TABLE, II ( 9) 

X-B 

Intel- :sau SinkMonth 

............... Convoy ligence 1ar Diaiz oonta.ot 1ngs 

A.pril BX 234 G Noo28o X-B to place 21/4 3 

1943 packo 

{ ctdo) BX 235 G Pack to Expeoto 

BX 236 N 

SC 125 G .. 

so 126 G 

so 127 G X-B pOSo & D1vers1ono 

so 128 G N'Oo )4o X•B pOSo to 

place paoko l/'j 

Olf 176 N NOo 2S 10/4 2 

ON 177 N 

ON 178 N NOo 29 .18/4 l 

ON 179 G 22/4 

ONS 2 If 

O.NS 3 N 

ONS 4 G NO., 30 23/4 

May BX 237 G NOo )So X-B pOSo S/5o9/5 4 1943 

HX 238 G 

HX 239 G No. 420 J: .... B pOSo 19/50 22./'i> 

HX 240 G 

BX 241 G 

so 129 G No. 390 ;x: ... B 

diversiono 11/S 2 

PllllC-NSS-'06 

'&Qi' SE6RI! T 0 p.1-SJ.E C R E T CANOE 
0 f-~F clJC: j.?~5-i;, .:) .U '-"' J. '-. L 

:rOJ:l SE6ffi'!l'i' (L0)227l-52 

SECURITY INFORMATION TABLE II (10} 

Month 

--- - May 

1943 

(ct:d.,) 

ic; ... __.30 

September 

;.943 

l'RNC-NSS-J06 

rpop SBG P.i1'f 

X--B 

I.ntelConvo1 ligenoe 

so 130 G 

SC 1)1 N 

so 132 G 

ON 180 G 

ON l8l G 

OM 182 G 

ON 18) G 

OM 184 G 

ON 185 N 

ON 186 N 

ONS 5 G 

Ol~S 6 G 

ONS 7 G 

ONS 8 G 

BX 255 N 

HX 256 N 

HX 257 ?l 

HX 258 N 

SC 142 N 

BdU 

war Dla:z oo.ntact 

No. 41. - x-B to 

plaoe paok. 18/5 

NOo 43 25/5 

X-B pos. No9 ops~ 22/S 

Noa 33. Ex.po 28/40 

Nov 36-0ontused with 29/.~~ ON 180 nearb7 4/5. S/S 

C/V of U·41S (6/5) 

and U-952 {8/;)e 6/5 

No. 40 1)/5 

Pack to o,perate. 

Sighted. No U/B9s 

available tor opso 23/9 

TOP1as16ECRET .. ~ 

81Dkiys 

if] 

1 
(L0)2271-;2 

SECURITY INFORMATION !AaLE II 1

111 

X-B 

Intel- BdU SinkAionth convoy .. -- ligenoe war Diarz Contact 1.ll§S 

16.,,30 ON 201 N 

Septe.moer 

194) ON 202 N NOo 4)o Dead Reek-

( ctdo) oiling plaoes pack to 

1nteroeBt• 19/9 

ON 20) N Pack plaoe4 bf X-B 

straggler .routeo 

ONS 18 N (Merged with ON 202).20/9 1 

October BX 259 N X-B ,Places gaok 1943 (CV evades)o 

HX 260 N 

BX 261 If Dead Reckoning pos. tails. 

HX 262 N 

BX 263 NH Deed Reok:oning pos. tailso 

SC 143 G Hoo 44a X\IDB Straggler Route (Cheok:s actual 

oo&trse· of O/V) o 9/10 

so 144 N X-B too lateo 

SC 145 N 

ON 204 G X-B: Straggler Route 

an4 I~endezvous. (OV c~osses pack line)o 

ON 20S .. N X•B latea 

ON 206 N x-B to plan attaoko 

ON 207 !l 

ON 208 N 

PRNC-NSS-'U 

T 0 -~ EC RE T.CANOE 5.1? SBQRBf 
(L0)227l-S2 

SECURITY INFORMATIO~l~LE II (12) 

Month 

October 

194) 

(otdo) 

November 

1943 

December 

1943 

PRNC-NSS-3'6 

EEnvor 

ONS 19 

ONS 20 

ONS 21 

BX 264 

IiX 265 

BX 266 

Bx ~67 

SC 146 

SC 147 

ON 209 

ON 210 

ON 211 

ON 212 

OMS 22 

ONS 23 

BX a68 

x .... B 

Intel= · .t1senc~. 

H 

G 

N 

N 

N 

:iq· 

N 

N 

N 

N 

N 

N 

N 

G 

oontao·t 

X0 B suspect deoeptiono 

HOo·4SQ X•B helps to 

place paoko 15/10 1 

:X•B lateo StrasgJ.er Route used to plaoa 

paclco 

Safs X•B gives routeo 

(Ho ev1denoeo O/V 

evades)o 

XoB: place 9aoko .Oon~ 

tact too late tor opso 

14-lS/ll 

X•B: place pack. 

Sa7s x ... B shows C/V 

South. (No evidence)o Attao~ unsuocesstulo 1)/1 

X-B too la teo 

X•B place pack. (O/V evades).· 

.· . ,. 
SECURITY .INFORMATION TAJlLE II (13) 

Mori.th 

---- = 

Doc ember 

3.943 

(otcla) 

9.~v~z 

BX 269 

RX 270 

:ax 271 

X=B 

Intel= 

!;§e.UC! 

N 

N 

N 

BX 272 :M 

SO 148 M 

SC 1.49 N 

ON 21) 

ON 214 N 

ON 21.5 N 

ON 216 N 

ONS 24 N 

ONS 25 N 

BdU 

\Yar Diary 

X-B: place paOko 

A/C recceo to place .paoko 

Dead Reckoning to 

place paoko 

Cohtact 

'2/,/12 

~=-=----------------------------------------------

PRNC-NSS-J&6 

January HX 273 N 

1944 

HX 274 N 

HX 275 N 

h"X 276 N 

SC lSO N 

SO lSl N 

ON 217 N 

ON ~18 N 

Northern U/B oontaotso 

C/V too tar North tor 

paok opso 30/12 

T 0 P S?.fi.€ R E T CANOE 

2 
(L0)227l•S2 

SECURITY lNFORMATION~1 ~1 <11.1 

X•B 

Intel-

'Mt.lnth CO.DVOJ' ligenoe ---- WWW I -¥- - Ja!l.u.arr ON 219 ·N 

1944 

( otdo) 

ON 220 N 

OiiS 26 N 

ONS 27 N 

February BX 277 N 

1944 

HX 278 N 

HX 279 N 

SC 152 .N 

so 153 N 

ON 221 N 

ON 222 N 

ON 223 N 

ON 224 N:. 

ON 22; N 

ONS 28 N 

OifS 29 N 

PRNC-MSS-3U6 

B4U 

J!!.r Dian 

u-960 sinlcs ship 16/16 ( Tllia sh19 

ill ON' 2l9Jo 

A/O sighting followed by U/B 0011-

tact next 4ay. 

contact near R'tdld. 

U/B oontaots~No attaoko paoJc to ogerate. Fails·. 

SinkOontaot J.ya 

16/l 1 

19/l 

9/2 l 

7/2 

U/B oontaot followed 

b7 ops by 7 U/B•s. 

:ra11s. 3/2 

10/2 

Escorts sighted. 10/2. ? 

X•B rendezvous to 

,plaoe pack. J'a1le4. 
SECURIT't' INFORMATION ~~ 11 .< ~>. 

March 

J~944 

PR llC-NSS-3G 6 

~P SEelUBi' 

X .... B 

Intiel-

~ !Yienc~ 

BX 280 M 

BX 281 

RX 282 

B 

N 

BX 283 N 

BX 284 

SC 154 N 

SO 155 N 

ON 226 N 

ON 227 N 

ON 228 N 

ON 229 N 

·ONS )0 N 

ONS )1 N 

Ddt1 

war D1a17 contaot; 

U/B olalma h1 t; on DDo 

(Bo record) 10/'J 

u/B driveA oft b7 

eaoor'o O/V not 

contaotec1o 

T 0 P Sefi-(I R E T CANOE 
ID:A65650 

Allll 2a2. PAY II DAI 811118Bt rE !EP!DR 

1Ffh OP .<Z p • I 

c ., 0 TA" LI mus 

I ff D118 1 2 ,Z HO 1 2 ' HO 1 2 ,J 4-l.O 1 2 l HR. 

I 

... llMClll 0 1· 0 4 ·o 0 1 , 0 ' 1 u 0 ' 2 20 rt t 2. 2 o- .0 •••• . 1. .. 0 0 ' 0 .,o O' ' - 3 0 0 l4 17 QI ,._ - 3 1 0 4 0 ='O ···o ·z 0 0 0 0 3 1 0 6 10 

s 4 2 2 0 2 0 2 0 1 0.1 0 0 2- ' 0. ·J JO ~ 5 0 0 0 0 ·o 0 0 1 0 0 0 0 0 0 0 1 1 

6 0 0 0 6 0 0 0 .6 0 0 1 13 0 0 l 2' 26 

7 0 0 0 0 0 0 0 , o. 0 1 s 0 0 1. 8 9 

a 0 0 0 0 0 ~O 0 0 0 0 o. 0 - 0 0 0 .0 0 

9 .o 0 ? 0 0 -0 2 0 0 0 lO 2 O' 0 19 2 - 21 

JO 1 5 4 8 0 2 0 2 0 18 ' 11 1 25 7 Zt S4 

u 2 0 0 1 o·o 0 1 ,, 2 0 , ' 2 0 9 16 12 I 0 0 .o .. 0 0 0 0 0 0 0 0 0 0 0 0 O· 0 

13 0 0 0 0 0 0 ·o ·o 0 0 0 0 ·O 0 0 0 0 

14 .0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

15 0 0 0 o· 0 0 0 0 0 o· 0 ·O o. 0 0 0 0 

16 . 0. '· 2 .. 4 -·.:.O 0 0 0 0 1· ,1 ·it Ct n '. ~i. 17 .1:. s I ' ' 0 1 1 0 0 1 •• 

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19 ·o 0 ·1 4 0 0 0 0 1 0 8 ,,. 7 0 9 43 59 

20 •. 0 J.,. 12 7 0 1 ' 1 0 2 ' 0 0 1 20 8 35 

21 ·. c 2 . 0 0 0 0 .o 0 1 0 0 1 1 2 0 1 4 

22 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

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25 '~ (; I .,) 6 0 0 0 s 0 0 0 6 0 o· 0 17 17 

26 0 0 (j 6 0 0 0 . 6 0 0 'O u 0 0 0 - 23 2' 

2'i \} .. a 0 0 2 1 0 21 12 2 0 22 l4 3 39 ·"!- .,,. 

28 "! -~ 2 2 2 1 0 0 ,. 9 1 3 l4 l2 ' ' 34 

29 s:. "l' t"': l 2 2 0 0 2 3 0 0 8 12 0 1 21 ·-- 30 2:1 ~ .. , .. ... 2 0 0 0 4 1 0 0 28 4 0 1 " "" .'!. 

31 "$ • J 0 2 2 0 0 1 0. 0 0 6 6 0. - 0 12 .. ... 

~1-:..--

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T'OTlL 216 '10 40, 6A9 6ft9 "'/' 

.. 

It •••• •' Y:? = & .. .,...... d&,.. .. ..... li&h!L4111:i:$ n:azr r¥P ';zar ..,.., ...... , , I 

·--~= "'' 1 

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REF ID:A65650 

AllEX 2020 DAY I! naY SUll!a!ll !! !BllmOIS 

.lam II -· •• ··p • c TOTALS mm.-. 

~·-DAIS lgr 2 l fslO· 1 2· a 'rl9 & ! 2 ti.· i 22 l I 3 .-Effl t 2 1 F :g •• 4 iUULl 0 1 0 0 o. 0 0 0 0 .0 0 0 0 1 0 0 1 . 2 0 0 0 . -.0 0 0 0 0 0 0 0 0 0 0 0 0 -0 

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8. 0 ·O 0 :0 0 0 0 0 u 0 0 u 0 0 0 0 0 

9 ·o._ 1 - 0 0 0 0 0 0 .. 0 0 a 0 ·o 1 0 0 1 

10 -o .. 1 ·_·o 0 '· 0 0 0 19 s 0 0 22 6 0 0 28 

u ·1. 0 0 8 0 ·o 0 4 12 0 0 I l3 O· 0 I .U. 12 0 ·2 6 ~1 0 0 ' 2 0 s 4 0 7 ·13 

13 ' 0 8 0 0 1 0 ' 0 4 0 ' 0. l3 0 8 21 

14 ·0.0 n .a o· 0 0 1 Q 0 " ,_ 0 0 ·O 4 4 

15 ·. 0' 0 0 0 0 n G 8 0 0 0 ' a· ... "" . 0 1? lf 16. 0 ·o · 3 l 0 1 ., 0 0 o· 2 4 0 1 8- ,. !.'· 17 l' 2 0 0 l 0 0 0 0 It 0 0 2 6 0 0 8 

JS 6 1 0 0 1 0 0 0 2 0 0 0 9 l 0 0 JO 

19 () 0 0 .0 0 0 0 a 0 0 0 0 0 0 0 0 0 

20 0 ·.2 ·l 0 0 0 0 0 0 2 0 0 0 4 1 0 ' 21 2 0 0 0 ' 0 0 0 30 0 0 o· 39· 0 0 ·O '9 

22 l 11 0 2 1 ' 0 1 10 2 0 2 u 16 0 

23 ' '' ' Q l 0 8 0 0 1 52 2 ; 2 6S 2 6 ' 76 

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25 9 0 1 0 9 0 0 0 l4 0 0 0 32. 0 1 o· " 26 2 0 0 0 2 0 0 0 4 0 0 0 8 0 0 0 8 

rt 0 0 0 0 0 0 0 0 0 0 0 0 0 . 0 0 0 0 

29· 0 0 0 0 0 0 o· 0 0 0 0 0 0 0 0 0 0 

29 0 0 0 0 0 0 0 0 . 0 0 0 0 0 0 0 0 0 

30 0 0 0 0 () 0 0 0 0 0 0 0 0 0 0 0 0 

· ~~ :1~1 te----~ .. tt_ ..... _.. . .t?r.-lL ... _L.........~~ ~~151 _ .n.~- 1• .. . 1361.22 M 211. .. 

.. TOTALS 130 . 81 416 627 :cs-:"'~L '? 

.. 

I ~:~~~~._.'='~~ ..... ..!'5~s1.=;:.~-:=.,:= .............. ,mta~~*'·'"ffell ... a.~ ... ;;K1J: .. : ... :=:- a 12 · .ca;•·= .... ~--;,;,:g;-.p:,:.. ~~~.· I 

i 
REF ID:A65650 

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nm or 

11•1JB p • c -

' 0 r A L s 1VlAt 

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• 

t·BY 

w 

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13 16 6 l ' i 1 0 0 ,. 13 1 2 ,,. 20 2 s 90 14 .4 u .Lo .4 0 0 ;; (i ~ t) i; 0 12 0 24 ,. . 40 Cf\ 

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20 l.l . ' ·o ·3. 0 4 0 0 .. ., 0 0 20 14 0 3 31 , . 2l g. 0 (). l 4 0 0 l 7 0 0 0 ·19 0 0 2 21 

22 :> 4 0 2· 0 l 0 0 ' 4 0 0 8 9 0 2 19 

23 Zl 2 ~ 0 4 0 0 0 ., 0 0 0 .;,i ~ 2 0 42 

24 e I• 0 'ii v. ..lo 1 0 0 0 0 0 0 0 9 0 0 l lO 

0 ,) ·'.? 0 0 0 0 0 .o 0 O· 0 0 0 0 0 0 - 0 0 0 0 ·"' 0 0 0 0 ·o 0 0 0 0 \> v (,) .... 

0 0 0 0 0 0 0 0 0 0 0 0 .o 0 0 0 0 

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0 0 0 9 0 0 0 0 0 0 0 1 0 0 0 lO 10 

0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 2 2 

0 0 0 0 0 0 0 0 0 ·o 0, 0 0 0 0 0 ·.o 

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ARNEX 2 .. 2 PjY B DAI"SfJllWa gf DJt;CRTPf;g<llS 

ff PE OF 

QI 

MESSA.GE p K c TOTALS TOTAL DELAY D IC 

·..\ DAYS i...z ,_, 6-10 u-1' 1~ ,_, 6-10 u-12 1-2 3-S 6"-10 11-12 1-2 ,_, 6-lo u-u 

""' QI 

QI -

JUD 1 0 0 0 0 0 0 .0 0 0 0 0 0 0 O· 0 0 0 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 - lj s 3 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

- 4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 s 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ~ 0 6 O· 0 0 0 0 0 0 0 ~ 0 0 0 0 0 0 0 o· 

7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 8 . 0. s 0 0 0 3 0 0 0 3 0 0 0 11 0 0 •.. ...... 9 .· 3 4 0 0 0 ' 0 0 0 0 0 0 J 7 0 0 10 10 

u .... 0 ·. 2 0 0 0 2 0 0 0 0 0 0 0 4. 0 0 4 ·· ..... =··: a.: o . · o 0 0 ' ~ ..... :. "'' 0 0 0 0 0 0 0 3 c 0 .3 12 ·. "' .. · 1 . .-... 0 0 0 1 1 0 0 4 1 0 0 It ~ 0 ·O 8 13 "' ~.= . ~:. 6. - 0 ... 0 0 1 0 u u ., 0 ,.. 0 l .o 0 0 1 14 -- .. :···;: o ~~a:·~ .. o .. ~ 

0 0 0 0 0 0 0 0 0 0 0 0 0 0 15· ... ·.' 0 . o:-. 0 " 0 0 0 l 0 0 0 1 0 0 0 2. 0 2 . 16 ·:,t, - 0 : {J ... 0 ... 0 0 0 l 0 0 0 l 0 0 0 2 0 2 17 :<.-: 0 =· O···"' 4 · . 0 0 0 2 0 0 0 0 0 .0 0 6 0 6 1s .-.~: ~···. o ·: 6 ~"'.o .. : 0 ·O 6 0 0 0 0 0 0 0 12 0 o· l2 19· · .. ·. : 0 •: l 0 .. 0 0 0 0 0 0 1 0 0 0 .2 0 0 2 · 20::-.:r o .·. o. o-.. :· .. 1 0 0 0 2 0 ·O 0 0 0 0 0 ' 3 21 : : ; o" " 1 · o · 0 0 3 0 2 0 0 1 0 0 4 1 2 7 22 ·.-..:: ... o... 3 -·~: .c 0 0 1 0 0 0 0 0 0 0 4 0 0 4 2j.: ... o .. ·.1: o· 1 c 0 .o , ,, 0 0 1 (1 1 .0 3 4 ... 24· • · o o···· a 2 0 0 0 0 0 0 0 0 0 o· 2 2 ..... ·,,.. .. · .., .. , 

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28 0 0 0 2 . t't n n n () ·l't 

.. n 2 

29 0 0 0 ·o o· 0 0 0 0 0 l 1 

0 0 0 0 0 0 0 0 0 0 o· 0 

J 1 10 50 r& I1 - I 

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lJ 93 9l .. 41 39 fl 

I 

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ANNEX 2c2 J21ll? D~I ,s.QJIWlf Ql..DECiV.TI,91'.J 

TYPE CF ~ MF.SSAGE p .I.I c 'l'O 'l'A LS TOTAL 

5'1 DELAY 

~ !!_QAJS 1.-..2 3-S 6-lp ll-lS 1-2 3 .. 5 6-lO ll .. 15 1-2 3-5 6-10 13:,·lS 11112 3-~ 6-10 ll-15 .. ....... I 

02 

_.2! JULY l 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

9 2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

3 0 0 0 0 0 0 0 0 0 0 " 0 0 0 0 0 0 - v 

4 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

s 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

6 t) {} 0 0 0 o· 0 0 0 0 0 0 0 0 0 0 .o 

7 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

9 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

10 ·o. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

ll 0 ·c 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

12 !) I) 0 l 0 0 0 0 0 0 0 0 0 0 0 l l 

13 "' .. 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 1 I 

14 o-o ,... 0 0 0 0 0 0 0 0 0 0 0 0 0 0 N 

u 0 

15 0 {1 u 0 0 0 0 0 0 2 0 0 0 2 0 0 2 "' J.6 0 Ci I',• 

\,J 0 !,) 0 0 0 0 0 0 0 0 0 0 0 0 

17 0 0 0 0 0 0 0 1 0 0 0 l 0 0 0 2 2 

18 - . 0 0 0 0 0 0 0 l 0 0 0 0 0 0 0 l l 

JS 0 1') v 1 0 0 0 0 0 0 0 l 0 0 0 2 2 

20 l) 0 l 0 0 0 0 0 0 0 (.> 0 0 0 l 0 l 

21 ·o 0 () 0 0 0 0 0 0 0 0 D 0 0 0 0 0 

22 c 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ·o 

23 ('", () tr 0 0 0 0 0 0 0 0 l ., 0 0 l l "' ..... 

24 0 (J 0 l 0 0 0 l 0 0 0 0 0 0 0 " 2 ""' 2; 0 0 0 0 0 0 l 0 0 0 2 0 0 0 3 0 ... 

~ 

26 0 0 0 0 0 0 3 0 0 0 l (J 0 0 4 0 I+ 

27 Q ,., ). 0 0 0 0 0 0 0 0 0 0 0 2 0 2 v 

2a 0 " • .. 0 0 0 0 0 0 0 0 0 0 ~ 0 0 0 0 

29 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

JO l 0 0 I'\ 2 0 0 0 0 0 0 0 3 0 0 0 .. \,." .., 

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TOTA!.S 2 0 3 4 3 0 4 3 0 2 3 3 s 2 10 10 ~ "' 

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14 · :·o ~ ~ =rY o · o o s o l o o o o ·O 6 o 1 

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20 .: .·o :·. ·2.-~- .o .-·:. l o 2 o o o o o o o 4 o i 

21 : ~~: o >:. o:"': · o ·~ ---: -o o . o o o o o o o o o o o 22--•::o-:··o-·ro·;. o o o o o o o o o o o o o 

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24_· ?:'..~o , o o o o l o o o o o o o l o· o 

as · :_- -o o o o o o o o o o o o o o o o 

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27 o·o i o o o o o o o o o o o 1 o 

28 0 . . 0 0 0 0 0. 0 0 0 0 0 0 0 0 0 0 

29 o o o ·o o o o o o o o o o o o o 

30 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 

31 0 0 0 - 0 0 0 0 0 0 0 0 0 0 0 0 0 -......------~-~.-.. ....... ........_ ... _......, .. .........,.,~---- ~ .... . -· 

TOTA'.i'..S 2 8 8 3 2 l4 5 8 0 3 3 3 4 2S l.6 14 

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;;o l 0 0 0 0 0 \) 0 2 0 0 0 3 0 0 0 .) 

31 0 0 0 0 l 0 0 0 l 0 u 0 2 u 0 0 2 -.. --. - ' .. -.a--·,.--- --·-·.,,....._._..-... -·--=---

'l'O'l' JiLS J9 6 0 2 .36 4 ;, 2 7 0 0 0 ~ 10 3 4 

TOTAL 47 45 7 99 99 z 

I 

_ ... ._ •• i=.:: ----e- --- Ii 

-- -··- .. ·- II: 
JJJI. l 

2 

3 

4 

s 

0 

7 

8 

9 

10 

ll 

32 

13 

)..4 

15 

lt> 

l? 

18 

l'I 

20 

21 

22 

2.3 

24 

25 

~6 

27 

28 

29 

.30 

.31 

l 

i 

5 

s 

b 

5 

8 

5 

4 

6 

s 

7 

;t 

5 

4 

6 

6 

7 

4 

4 

J 

5 

.. , 

7 

6 

6 

5 

9 

5 

5 

2 

0 

u 

l 

0 

0 

0 

0 

0 

u 

l 

0 

0 

0 

0 

l 

0 

\) 

0 

0 

0 

u 

0 

0 

IJ 

0 

0 

0 

0 

0 

() 

0 

.P 

3 4-10 

0 

0 

0 

0 

0 

u 

0 

-0 

0 

0 

0 

\) 

u 

0 

0 

0 

0 

0 

0 

0 

0 

u 

u 

u 

0 

0 

0 

0 

0 

u 

0 

0 

0 

L) 

0 

0 

0 

\) 

0 

0 

0 

u 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

l) 

0 

l 

0 

2 

0 

0 

1 

0 

0 

l 

CJ 

0 

3 

2 

4 

l 

l 

l 

l 

2 

2 

u 

3 

l 

2 

0 

l 

5 

l 

l 

3 

0 

3 

2 

u 

0 

0 

0 

\l 

0 

l 

0 

0 

2: 

0 

0 

0 

0 

0 

() 

0 

u 

0 

0 

0 

u 

0 

0 

0 

0 

0 

l 

0 

IJ 

0 

c . TOTALS 

.3 4-10 l. 2 3 4-lo l 2 :; 4-10 

== ±ft' Ldii:iictt± *A z 

0 0 0 0 0 0 2 0 0 u 2 

0 0 0 0 0 0 7 0 0 0 7 

0 0 0 l 0 0 s 2 0 " 7 

0 0 0 0 0 0 6 0 0 0 6 

0 0 0 0 0 0 6 0 0 0 6 

0 0 0 0 0 0 8 u 0 0 8 

u 0 \) 2 0 0 5 3 0 0 8 

0 0 0 0 0 0 5 0 u 0 s 

0 (,) l 0 0 0 7 0 0 0 7 

0 0 0 ;t IJ \.) s 5 0 0 10 

u 0 l 0 u 0 ll 0 0 0 ll 

0 u (,) u 0 u 4 0 " 0 !; 

0 0 0 0 0 0 9 0 ~ 0 ~ 

0 u l u 0 0 b 0 0 0 6 

0 () .l u u 0 8 l \) 0 9 

" u u 0 0 0 7 li 0 0 7 

u 0 l 0 u 0 9 0 0 u 9 

0 u l 0 u u ? 0 0 0 7 

0 0 0 0 0 u 6 0 0 0 6 

u u 0 0 u u 3 u 0 0 .3 

u 0 u u \) 0 8 u 0 0 8 

u u () 0 \.I i.) 8 0 u 0 8 

0 0 l u u U J.O O 0 0 l.O 

0 0 0 u u IJ Q 0 0 0 6 

u u J u u u 10 0 0 0 10 

0 0 0 0 u 0 10 0 0 0 10 

0 0 0 0 0 0 10 0 U 0 lU 

\J u ; ;( l l) 9 3 l u 1.3 

0 0 3 0 0 0 ll u 0 0 ll 

I.) 0 0 u u u 4 0 u v 4 

u u l.} iJ u lJ 9 (j u 0 9 : _____ __.._,__ _____ Ja-1•n- ••••- :s-·n-•-------...,.--------·-·....,- -•• -.. ·--·------------~----=------=-.... ._. _ _,_.11.- C'j' 

., 

'i'OT.hf·b 161~ 3 0 0 /~l. 4 U O 16 'l l o 2;;!J. li+ l i1 .._ ... ,_, ___ .l'O.:.l---T--... -· ... - ... &............ _111--.-~=-- ~ - .... ..,._...,. __ ..,._.:0-_11 .... .-_.,.;:..._-..a .. - .... ._ ----- 0 v .. _ ---------------------~ If 
l!l!.B. l 

2 

3 

4 

5 

6 

7 

8 

'l 

0 

REF ID:A65650 

l 2 34-10 l 2 3 4-10 l 2 3 4-lO c:ee 

5 0 0 0 0 0 0 0 0 0 0 0 

8 l u 0 2 u 0 0 0 0 0 0 

5 0 0 0 2 0 u u ~ u u \) 

9 0 0 0 l 0 0 u bu u u 

1-J 0 0 0 0 0 0 0 l 0 0 0 

9 0 0 (J 2 0 0 0 l 0 0 0 

10 0 0 \) l 0 0 0 2 0 0 0 

8 0 0 0 0 u u \) 5 0 0 u 

7 0 0 0 0 0 ;t 0 2 u l 0 

l 6 0 ·l l l 0 0 s 4 0 0 

"J u 0 (J 0 0 u 0 l 2 l 0 

0 5 u 0 0 l 0 0 0 l 0 " 

:lJ 6 0 u 0 0 0 0 u 0 l u 0 

14 6 u 0 0 2 0 0 0 0 0 0 0 

15 6 0 0 0 0 ~ 0 0 l 0 0 0 

16 6 0 l 0 l 0 0 u 2 0 0 0 

l? 4 0 0 0 ~ 0 0 0 0 0 0 u 

18 8 0 0 u 0 0 u u 2 0 0 u 

19 ll 0 0 0 J ;c 0 0 ll l u u 

20 6 0 u 0 2 0 0 0 2 0 u 0 

2l ~ l 0 0 0 l u 0 l 0 0 0 

22 ll 0 u 0 1 v u u 0 0 u 0 

23 5 0 0 0 0 0 0 0 2 0 \) 0 

24 8 0 0 0 0 0 t) 0 0 " u 0 

25 8 0 0 0 1 l 0 0 0 0 0 0 

20 7 o o o o u u u o u u u 

2'l J 0 0 0 0 0 0 u 0 0 0 0 

2g 5 0 u u l u u 0 0 0 0 u 

_£L__ _ _L,_ll __ ,.Q_ 0 M•l __!L_J) 0 ____ q___y __ o 1 

:r 0 T A l. s T01'JIL 

1 2 .3 4-10 

s 0 0 0 

10 l 0 0 

9 IJ u 0 

lb 0 0 0 

10 u 0 0 

l2 0 0 0 

13 0 0 0 

].) 0 0 0 

9 0 3 0 

7 ll 0 l 

10 2 l 0 

0 7 0 0 

6 l 0 0 

8 0 0 0 

'l 

9 

6 

10 

25 

10 

4 

J2 

2 I.) 0 

0 l 0 

0 0 0 

0 u 0 

.) 0 0 

0 0 0 

2 u 0 

0 0 0 

0 0 0 

0 0 () 

l 0 u 

0 0 0 

,, = 

s 

ll 

9 

16 

lO 

l2 

13 

l) 

L! 

19 

l) 

7 

7 

8 

9 

J.O 

6 

10 

28 

10 

6 

l2 

'"I 

8 

J.O 

7 

0 0 0 ) 

t> 0 0 0 6 

6 _Q__~_q__!, ______ __:i._~T-., 

T·\TL.L!-' l!V" ,'l J. ] ''3 n , _, ,-. l ~v ~-;;;i -'~ Jo; - • r. \3 2 tJ 4ti 't ;?. • 257 JO !i 2 ... - .. ·----.. ._ ... --.--...._.._--,~ ...... .._. ____ ,...,,-_..,._ic. _____ ~---- ______ .,....,.,. ___ ... _ __..___...,... ______ .,._-., . ..,.. ........ ,._ • --.--~r_...:.,~r..~ 

~':i 

·- --...:.::.-~-~·-·-----~--
REF ID:A65650 

.. Al 2.2 tf4I Bl ll@.X taYl!IMI gr 8ACKD'T.1Ql!e; 

~Itii O!' 

I ~ 111· c !OtaJ.& TOTAL 

fX u~ 

a~ 1 2 3 4-10 1 2 3 4-10 l 2 3 4-lO l. 2 3 4-10 

..\ MJthCH l.- 0 2 3 1 0 u u 0 0 0 I.) 0 0 2 3 l 6 

~ 2 5 fJ . l. u ].. 0 u u l 0 u u 7 0 l. 0 8 

3 4 0 1 (> 1 0 u u 0 u " 0 5 0 l 0 6 

4 0 4 l 0 0 1 0 0 0 l 0 u 0 b l 0 7 

5 6 0 u 0 1 0 u u u 0 0 u 7 u u u 7 

& 4 0 0 0 0 u 0 u 0 0 u u 4 0 u 0 4 

7 5 0 0 l 2 0 .U 0 u . \J u 0 7 O· u l 8 

8 6 0 0 0 0 0 u u fJ 0 u u 6 0 0 u 6 

9 8 u u u 1 u. tt u 0 u u 0 9 0 u u 9 

10 7 2 u· 0 0 0 u u \) 4 0 u 7 6 0 \) l3 

11 4 u u. u u 0 0 u 2 u u u 6 u u 0 6 

12 4 u u 0 u u .0 u l u \) u 5 0 u u 5 

13 6 0 0 0 ;t u \) u 2 0 u u 10 0 0 0 10 

14 ., 0 0 ·O l. 0 ij u 0 0 0 0 8 {). 0 0 8 

15 6 0 u 0 0 0 0 u 0 0 u 0 6 u 0 (; 6 

16 6 0 0 0 0 u u u 0 0 u 0 6 u u u 6 

17 ' 0 0 0 l 0 u u l 0 0 0 7 u 0 0 ? 

l8 5 \) 0 \) 0. 0 u u l ij 0 u 6 0 u 0 6 

19 2 0 0 0 l 0 0 (J 0 0 u u 3 0· 0 " ;; 

20 s 0 ·O 0 0 0 0 u \) u u 0 s u tJ 0 s 

2l. .3 0 u 0 fJ 0 u .:i u u u u 3 o. u 0 3 

22 7 0 u u l. 0 u 0 u u u o. 8 u 0 0 8 

23 6: 0 o· 0 0 u 0 u 0 0 u u 0 0 0 0 6 

24 7 u 0 0 0 0 0 0 0 0 u 0 7 0 0 u 7 25. ·s 0 u .0 0 0 u u l IJ u \J 6 0 u u 6 

26 7 u 0 u u u u u 0 u u I.I 7 0 \,) u 7 

2.7 " 0 (J 0 t) u "' u .1. u 0 u 7 u: u ·u 7 

28 ~ u u u u u u u u iJ 0. u s v u v s 29 J. 0 u u 2 u v u l u l)i. 0 b 0 u 0 6 

Ju s u (J "' l u IJ u 0 u u u b 0 \J 0 6 

l u 0 .u 

- 0. 0 " Q u 0 iJ u 5 u u u s .. v .. 

'I' 

:CuT.1\Lb 154 8 6 .. 2 l~ 1 u 0 ll s 0 " 18\J l4 6 2 fl 

I 

Ill 

16 16 IE TOTAL 170 202 2~ 
PRNC-•SS-J'6 

lQ Annex 3 contains the following: 

(a) Basic onerational data used 1n the calculat1on 

of contact probabilities and contact coefficients, 

Tables l and 2; 

(b) Contacts per convoy day per U-Boat day, for 

monthly intervals, and averages for neriods, 

Table 3; 

(c) Contact coefficients for monthly intervals and 

averages for periods, Table 4o 

(d) Data on attacks and ship s1nkinge, Table 5a 

2~ !n comnuting contact coetficlents, equation (2) of 

Part 3 of the text is used; namelyg 

where 

" = CA ~ ft 

Q • the coi1tact coetf1c1entD 

A = the area under consideration; in U11s 

study, the region lying between 40~=630 N, 25•-soow and 48°-63°N, 

150-25°W; roughly, 3 million square milee; 

N • the average number of convoys in the 

area during a given intervalc Thia 

ouantity was determined from the Cominch 

daily plots or submarine and convoy 

t>OSitionso 

T = the number of U-Boat days s:oent 1n the 

areao Thia quantity was determined from 

the dally listings in the BdU War Diaryo 

C = the number of convoys contacted by the 

U-Boats during a given 1ntervala NOTE~ The term 11 contact 11 is used in 

the sense thet a given convoy is con= 

tacted only once, regardless of the 

number ot U-Boe.ts that actually contacted 

1to This rule is adhered to even 1n the 

case of a convoy that, having been once 

contacted and subsequently lost, was 

recontacted laterp 

TOP S ~CR ET .CANOE1 
(L0)22?1-52 

The value used for the number or contacts, C# 1s 

obviously a very critical quantity 1n the determination 

of the contact coefficiento The chief source ot 1nforma t1on on convoys contacted is the BdU War D1aryo 

•rne U-Boats were required to reoort every sighting 9f' 

a convoy, and the War Diary consistently mentions these. 

In doubtful cases a check is provided by comparing the 

renorted location of the contact with the nos1t1on of the convoy given in the da117 u-Boat plots: which also 

plot the convoy positionsa In a few cases 1n which the 

War Diary was uncertain whether a contact (or attack) 

was on a convoy or an independent, the IBM listing of 

ships sunk 1n convoy and the Convoy & Routing Jacket 

of the particular convoy furnished a clue" It is believed that any errors in the determination of the 

number of convoys contacted are so small as not to 

significantly affect the average values of the contact 

coefficients for the three Periods I, II, and IV, and 

hencea the general conclus1ona stated in the reporto 

7np ~~l&'f )0 ... 2 PRNC-MSS-3U6 

T 0 P S E C R E T CANOE 
9f ~F );~~~~~ . Ot' ~:CtK 

SECURITY TNf ORMATION . (ID)2271-51! 

!QLJi 1 

BASIC OPERA'l'IOlfAL DA.'1:6 

Awrce 

Oonvor Wet.of U-lcat Ships 

HOil th CoD1'9}'B l?gt - Copqq pay, __ Cptp.gt;g hp]s 

1942 J'U.17 18 2216 1.0 506 2 7 

Avgust 17 226 7.3 Ill 6 19 

Septem.'ber ii 26o s.1 u5s 1 20 

October 224 7.2 1411i 7 23 

1lwembet' 11'. 

~ 1.0 8\5 1 2S 

December 16 s.o ,-1 

Total 100 llf?l i.6 5675 n 121 

- - 1943 Jamiar7 16 fr. 1:6 ~~ l ~ 11 a W"DB.?'J' 11 

March 16 239 7.7 1741 s 

April 16 1811. 6.2 1594 8 20 

Mq 20 252 s.1 1733 9 19 

Toi!!l n J;o65 z.:1 ze 311 :lid 

Sep. (16-jO) 12 103 6.9 .~ 3 6 

October 201 6.5 2 IIWoTember 12 11'2 lf..8 810 2 0 

December 13 169 5.6 852 1 0 

19'4'4 JamJa~ 12 168 5.6 l~ ' 3 

Peib!'\'l8!97 12 1116 5.0 1 

March 13 159 5.1 676 l 0 

Total !I 1088 5.6 ' 51116 i6 I~ 

G.t-tAnd Total 266 3514 6.7 lS.,666 91 263 

°Fst:1t'lated. llecoraa of 16/10-)1./10 DOt aftlla'bla. 

~eP SEeftft )o-) PR NC -NS S _,U T 0 P S E C R E T CA~OE 
:-.. ~A:BLE 2 

BASIC OPERATIONAL DATA W!Tn RESPEC'l' TO COMPROMISE '.B'f X:.=B Imn.I.XGENOE 

C\J 

It'\ TOTAL NOT COMPROMISED CO!<~OM'i:§lllD _= il'o~&J: 

~ Average AveiPaga Averagra 

~ No. of Convoy Noo of No. ot Convoy No. of No. of Oamo;r Wo. of 

(\J 

-0 

H 

!!£ M.on11,h .Q,Q.nvon ~ Convm ~lii Oonvo:rJt l?ge ContQJ:a Cont&.o.tm. ~p.VOK9_ ~~ Q.9Jl~ ~ 

- 1942 Ju17 18 246 SoO 2 11 151 4.,9 0 1' 95 . 3.1 2 

August 17 226 1o) 6 9 116 308 a September 19 260 807 

g 110 Jo5 3 - 1 12 161!. 5.,5 1 96 302 3 i • 

October 16 22~ 7o2 -7 14 200 6e4 6 2 24 - OQS l 

November 1~ 209 7o0 9 8 124 4o2 6 6 g5 2oS ' 'December 16 196 SoO 6 9 Fn. 2o7 2 7 115 ;:r i It) ~ 

"° Total (100) (1361) C7o6) (37) {63) (g36} {~aI2 (21} (312 (5..25) (?e9) - {l§l ~ () 

1943 JaDIUU'7 16 222 7o) 7 6 123 4ol l 10 99 302 6 

February 11 16g 600 6 6 95 3.4 3 "" 1a 13 206 

Mar ~ I oh 15 227 7,,3 1 1 17 0.55 1 210 6oS 

AJ»:"il 17 196 605 9 6 Gs 2a3 2 11 126 4o3 1 "" 

~ May 2o 252 3ol 9 3 ~? Oo7 1 17 230 7o4 fJ 0 

CJ 

Total (79) (1065) (7,1) (381 (22) (325) (2,.g) (8) . (57) J74o) (429) (30) (\J --t 

0 

Sap.(16.,30) 9 103 60.9 3 9 103 6.9 3 0 0 0 0 (!} 0 rl ~ October 16 201 605 2 13 160 5oJ 0 3 41 la3 2 ~ November 12 14E 4 .. 8 2 12 l~. >+oS 2 0 0 0 0 E-4 

December 13 169 506 1 12 156 5..-2 l l 13 Q).j. 0 - JenUB.1'7 . 12 . 168 506 ~ 12 168 506 3 0 0 0 0 

February 12 146 5.,0 12 lij6 5.,0 4 0 0 0 0 

March l) 159 5.,1 l 13 159 5 .. 1 1 0 0 0 0 

Total (ITT) (10St5) (506) (16) (g3) (lQ.3~) (5 .. 3) (14) (4) (54) (Oa~51 {22_ 

G1•and To·t!!JJ. 266 3514 601.\. 91 16g 2195 4o0 43 98 1319 3aJ 48 
!ABLE 2 (ContiDMA) 

llASJC OPJllATIO!AL DA.TA Wl!R PRIO! 'l'O COMP!OMISI :BY x..:e lmlWGE!CE 

I\ Deatgnated 'bJ Wot Deatpatecl 'bJ' 

J. OOMPllOMldD: 1411 tm: ggsu&o1 OOIO'ROMISID: •a for S211mH21 

,_ ATerao AT81'ag& 

~ Ho. of Con.vo7 :lo.of Wo. of Conw;r 1ro. of -0 

~ I!E Ho1th gopyoz1 DftYt 2s>noz1 Ooptagtg oavors DRI Conyoz1 Ooatact• 

- 191J2 .T1l17 0 0 0 0 1 95 3.1 2 

August 1 18 o.6 1 7 92 2 .. 9 2 

September 0 0 0 0 7 96 3.2 3 

Octobal" 0 0 0 0 2 24 OoS l 

lloY•'b• 1 12 o.IJ 1 5 73 2 .. 4 2 

Dec•'b• 1 8 0.3 1 6 107 3.4 3 

!oal {32 tJll lo.g} '3l 'El {!Jill ,2.zl ,131 

l9li3 J8D'Da'17 3 l; 1.2 3 7 61 2.0 3 

Yeb1'U817 l 1.5 2 2 30 1.1 1 

March 82 2.6 It. s :i;;s 4.1 2 

April ~ 39 1., 2 8 l= l·o 5 

Mq 81 2. 6 11 .s 2 

~ota} '212 ~2832 ,1.~} '1zi I (36} '!t5.z2 ,3.0} ,132 

'""'. ( 16-3C>) 1 (c) 13 (o) o.g 0 0 0 0 0 

October 7 (o) ~ (c) 2.0 2 (a) 0 0 0 0 

llOTall'b.- 11. (a) (o) 1.5 1 (b) 0 0 0 0 

Deoembc 2 (o) 27 (o) 0.9 0 0 0 0 0 

January 0 0 0 0 0 0 0 0 

l'e'braa17 l (o) 12 (c} o .. 4 0 0 0 0 0 

March 0 0 0 0 0 0 0 0 

! 

Total (15)(4) (159)(0) (1.2}(c) (3) 0 0 0 0 

{4J,•l . ( ~4 H rt1-___ ~fiH el {2} 

39 (d) 480 (d) lo2 (d) 23 70 944 (e) 2.,8 26 

28 (e) p5 <a> lo2 (a) 22 

:: 

'i' 

"' IC 

I 

!i 

f 
i.PQP RCQl' 

SECURITY INFORMATIOr~· 

(L0)2271-52 

PUC-NSS-3U 

(a) lat:l.mated. !he llcJU dlar.r from 16 October 1943 to 

31 Oato'b• 19~3 is not aY&Ualtle. 

(b) JdtJ peaaecl the aom07 !'OU• oonac•"7 fltom ,,.,,. 

acant7 '1-11 !atelligenoe cm •-..i••' TO•tea. 

(o) Vam'bara deat1rDated bi' (a) 'P91'td• to co11Y079 wbtoh. 

l:n the 41ar70 MU menttoa epeelfiaall.7, ata,lq 

that l:i-'B "t)t'OTlded. so• 1Dformt!on tbat t.:dluenced 

his dt.Rpoai tion of the U-Boat groap1. Dari11g 

Period. IV the intellt.gwmoe &Tatla'ble to 'Bdl1 oomalnect 

on17 scaat7 informat!.on conael'll1ng atramler routn 

and earl.7 rendesv0118. aome of vldcb wa actual.17 

false. !he mmbere clvea ln the 8 COMPROllISE1).Jl'MA.L 

column• pertain onl.7 to tl»ae COB't'n78 for whlch the 

ev1denae indicates that X-B aetu.'\l]T bad usefUl ~ 

intelllpnce. Thia aplatm the dlsarepAJlCI between 

this col'UllD and the nezt om. 

(d) !l'hese mmbera B!'e baae4 on the nambera nplal:na4 

in (c). 

(a) !'heae Dab81'a 81"8 based on tbe f'1gares in the 

"OOMPROMIRD-'l'O!'A.L colan•; t.e •• the 'Pal'tlc'Ular 

CODYOJ'& are constd.ered to bata bean actu'lll ~ 

C081pl"Oll!8ecl b7 tbe X-ll aftJ.J.a'ble. 

)o-6 

T 0 P S E C R E T CANOE 
tAflld!, l 

OOHT.aCTS Pi.It C~VOY De! PJtik IJ-JK>nT DAY (p) 

.!!!!: Month Po pl P2 !1 ~ Note@ 

(Jllult1P4r eJ.l numbers by io-4) i 0 • Cont&cta 981' CmT07 

191.2 July 0 l.2.6 (1) 12.6 4.8 Iiq per u-aoat conAUg. .,.6 10.2 20.7 a.1 9.9 sideriAg onl.7 canSept .. 6;3 s.1 (1) 8.1 6.9 voys not. compromiaed 

Oct .. 6.,3 9.0 (i) 8.'7 6.6 by X-B intelligence. 

Noy. 17.l 12.6 29.7 9.6 l5-3 

Dec. 7.8 11.1 39.9 9.0 . 9.9 Pl =. Contacts per Con'V'Oi)' 

Average 8.1 9.9 28.0 8.6 8.8 Day per U-8oat considering only om194.3 Jan. 2.1 14.7 19.2 12.0 7.8 voys compromised by 

Feb. 6.,3 8.1 9c0 6.6 6.9 X-d intelligence. 

Mar. 10.2 4.s a.4 2.7 5.4 p

2 s Contacts per Convoy Apr. 5.4 l0.2 9.6 10.5 8.7 Dq per U-Bo1r.t cOllMta.y 7.8 6.0 12 .. 9 2.4 6.) sidering only thoee 

Average 4.7 7.8 ll.5 5.5 6.9 compromised convoya 

Sept. s.o (1) (i)(e) Od (~~ 8.0 specifically designated for oper11.tions Oct. 0 J.7.0 17.0 (1 ,3.6 by BdU utilizing .Nov. 5.1 (1) (i)(e) tS.4d (1) 5.1 X-B intelligence. Dec. 2.4 0 0 (i) 2.1 

1944 Jan. 7.5 (i) ~i)(eJ (i)d (i) 1.s P

3 'S Cont1&cta per CODVOT 

Febo 12.0 (i) i)(e) Od (1) 12.0 Da,y ,&1er U-J:loat conMb.J'o 2.7 (1) (i)(e) (i)d (1) 2.7 .sidering only those 

Average s.6 l,3.4 l3.4(e) 6.Sd (i) s.6 convoys compromised 

by X-B Intelligence, 

Average !or but not s,t>ecific&lly 

Entire Period 5.s 9.5 14.Se l.).2d 6.8 7.8 designated by Bd1J £or 

operti.tions. 

P • Contacts per ConYOy 

(i) ~Indeterminate - i.e., there were no Day 99r U-Boat conconvoys of the respective category sider.lng l&l.l convoys, 

present 1n the area during the period compromised or not. 

in question. 

(The source for data for 

(d) 5. (See Dote (d) on Table 2 of &mex J) if 2 ad P3 ia the War 

(e) s (bee note (e) on Table 2 of Annex 3) 

DiU7 ot BdU.) 

PllNC-NSS-346 

' T.O p S

0

E c RE 't~OANOE 
er 0 ~F ~DyJl~~O...,& r "ncm 

i'0f Eih6Bi!fl {L0)22'71-52 

SECURITY INFORMATION TtMJ·• 4 

CONT.aCT cupl'1CIPL"6 (¥} 

Ye&l.• Month 

-

"o (~ ~ ~ "' mU8a per DBi> J.9~ cluly 0 3800 (i) JCjOO 

August 2900 3150 6400 2500 

Se9t. 1850 2400 (i) 24,a 

Oct. ~ 2650 (i) ZIOO 

Nov .. SlOO 3800 8950 2900 

Dec. a3SO 3450 12500 2750 

Ave.rage 2450 2950 8400 2600 

19.43 Jan. 600 45SO 6000 7100 

Feb. 1750 2250 2500 1850 

Mar. 3lSO 1500 2600 850 

A.pr. l.600 ,;uso 2900 3.l.50 

May 2450 18.50 4000 '150 

Average 1400 2350 3400 1650 

Se9t. 2350 (1) O(d)(i)(e) U.J 

Oct.. 0 Sl.00 5100 (1 

Nov. lSSO (1) 2500 d i e {l) 

D<iCo ?00 0 0 (i) 

1944 ,J i&.11. 2250 (i) (i){d)(,)(e) (1) 

}'eb. .3200 (i) O(d)(i)(e) (1) 

Mar. 850 (1) (i)(d)(i)(ej (1) 

Average 1550 4050 2050(d) (1) 

40SO(e) 

Airerage for 

Entire Period 17.50 2850 .3950(d) 2050 

.44SU(e) 

(i) ":a Indeterminate - i.e., there were no 

convoys oi' the res;ective cateiOJ-7 

present in the area duriDg the perioci 

in question. 

(d) 5 (See .Note (d) on Table 2 of sm.nex 3) 

(e) 1J!!! (See Note (e) on Table 2 of &nnex 3) 

]o-8 

-"' 

1450 

JOSO 

21.00 

2050 

4SSO 

2400 

26'° 

2300 

19SO 

1'100 

2600 

1.900 

20SO 

2400 

llSO 

l.SSO 

6SO 

2300 

.3500 

8SO 

l?OO 

2350 

<.0 s Contact Coe1'ticieat 

considering an.13' convoy& no~ C0111promieed 

by X-8 intelllgenoe. 

~a Cont.ct Coeti'icient 

COl1&1der1Dg onl¥ Ul. 

convoys CGal!lZ'Gllised b,r· 

x-a intelligence. 

2 5. Contact Coeti'1c1ent 

considering only' thoae 

convoys a~c11·1call.7 

designated. for O.li)~ra. 

tiona by J:IUU utiliaillg 

x-a intaW.gence. 

Q3 • Cont&ct coefficient 

considering only tho• 

convo;ra coml)romiseti b7 

X-B intelligence, bilt 

not d.esip&tea as such 

by BdU. 

{If '; Contact caefticient 

considering &l.l convoys, 

conagramiaed or no~ • 

('l'he aource tor &.teL for 

"2 and "3 1• the War 

Diary of ~dU) 

TOP SE ERE TcANOE 
(\I 

:.c-.. 

p 

M 

,._ 

l"IJ 

C\I 

, ... (.) 

~l ...... July 

August 

sep~,ember 

October 

November 

Dacember 

Total 

Janua.r7 

'.D'ebr~..ry 

Mm" oh 

Apr!.l 

M&7 

Totr..l 

"IP. --

Sep. (16c--30) 

October 

!lovember 

December 

Jamiar1 

ll'ebl:1U9!'7 

March 

Total 

REF ID:A65650 

=-------~---~VERA.LL -i=tt;;;;;;a ... ck_s __ S_hi_p_•_SU!ikCs>nvOJ's Oontacts (n.) (b) '! (a) (b) '? Convo1's w I em -=--==----- ~--

18 

l.T 

19 

16 

14 

16 

100 

16 

ll 

15 

17 

20 

I_q 

9 

16 

12 

13 

12 

12 

13 

§Z 

2 

6 

1 

7 

l __ 31 

::s 

2 

2 

1 

' 1 

16 

91 

2 0 

2 2 

:; ) 

~ g 

3 2 

15 _16 

3 

2 

11-

3 

2 

l 

3 

2 

2 

4 

6 

6 

8 

5 

31_ 

6 

6 

g 

4 

14 13 27 

· 1· 

t 

0 

0 

0 

0 

0 

1 

l 

0 

0 

2 

1 

0 

2 

2 

2 

1 

? .. 2- I. 

7 

15 

18 

19 

21 

22 

l.Q2 

18 

18 

~, 

13 

17 

1Q9. 

5 

3 

0 

0 

0 7 11 ~ 19 9 

3 21 12 

4 23 14 

T 2s 8 

3 25 9 

21_w 63 

4 22 6 

5 23 6 

l lt4 1 

4 17 6 

3 20 3 

1L.Y.l __ ~ 

l 6 9 

l 4 13 

3 

l 

3 

1 

6 11&. • ..... wmi. 

12 

12 

12 

12 

13 

81 

16S 

AttRcks 

Conte.eta (a) (b) 'l' ---- ..,_._ c=-=-

0 0 0 

~ 6 

6 

2 

1 

3 

1 

2 

1 

_s 

3 

0 

2 

1. 

~ l 

1 l 

2 l 

3 3 

11 2 

13 l. 

19 4 i~ 23 

0 ; 5 6 

?. 0 2 

0 6 

9 0 9 

3 ).0 18 ~- 11• ,.2 1] 65 

1 0 l 3 

2 l 3 18 

0 0 

0 2 2 0 

0, 0 

3 ..3. _§ D 

1 1 2 5 

0 0 

0 u 

0 0 

0 2 2 0 

0 1 1 0 

0 0 

l ~ ~ _92 

0 .3 

2 20 

3 3 

1 6 

3 3 

l 1 

12 17 29 7'1 23 101 

Attacks Ships Sunk 

Oonvoya Contacts (e.) (b) IJ.' _ (a) (b) f -=rwww ~ ~~~~~~ 

7 

8 

1 

2 

6 

1 

.Jl_ 

10 

l~ 

0 

3(e) 

0 

1 

0 

0 

0 

4 

2 

3 

' 1 

~ 16 

6 

g 

7 

s 

2 0 2 1 0 7 

l l 2 4 2 6 

1 2 3 5 2 1 

0 0 

2 l ) 21 

l 2 3 13 

L..,6 11 50 

2 

0 

4 

3 

2 

5 

3 

' 4 

1 1 2 3 1 

l 1 2 3 l ..! 

(Table 5 Continued on Dext page) 

Att~wks ~·iolding 3 or moro sinld!!,ggo 

Ai.~i.iaeks yieldi.ng i ... 2 sinkinge • 

.i\~tta.clt9 yis:t.di211: at lea.st one si:nld~. 

!~oto: Only those attacks ;:;lelding e.t least o:ne si.nld.ng are cons1daa'ad. 

(d) Soe Note (d) to !able 2 c~·Annes 3. 

(e) Saa Note (0) to Table 2 of A~~~ j. 
REF ID:A65650 ~ABLE !2 ~CgntS:nued) 

~TTACX§ AND §!!IP Simt:IlUS 

Design.a tad b7 1'dlJ Bot Designated 'b1 :BdU 

OOMPROMISDD: for 9.1!aratlcm1 COMPROMISED; '9E 2Q1r1~1onn 

~ Attack a Ships Sunk Attaab Ship11 Sunk 

e 9.gnvoYI C2niaci- ill !ll ..'L w. l.1?.l. ='- Q.,nm:oza .2Amaaia .w.. .OU. ....L. .W. !J!l L 

1942 JTJ.l.y 0 0 0 0 1 2 2 0 2 { 0 

C\J ~ - Auguat 1 1 0 0 1 2 l 1 2 2 

0 September 0 0 0 0 7 3 1 2 3 5 2 1 ..:I 

- Ootober 0 0 0 0 2 l 0 0 

Jlovember l 1 1 0 1 16 0 16 2 2 l l 2 5 l 6 

• Decemi>er 1 l 0 0 3 l 2 3 13 3 16 

Total 3 3 l 0 1 16 0 16 3!! 13 6 6 12 !~ g 4g 

1943 Jan'fJ8r7 3 3 1 2 ' 12 2 11'- 7 3 1 l 2 3 2 5 

J'ebl'U8!7 g 2 0 2 2 0 2 2 2 1 0 1 t'. 0 1 1 

Ma.rob "' 4 0 4 43 0 43 s 2 0 1 1 0 1 1 

April a 2 1 0 l ' 0 3 s 5 2 1 3· 10 1 11 

Mq 6 1 2 3 3 7 11 2 l 0 1 13 0 13 

Total 21 lI 1 6 13 62 I 6~ 36 13 4 4 g 2§ 2 31 

Sep.(16a30) l(d) l(e) 0 0 0 0 0 

October 7(d) 3(e) 2 l 1 2 3 l le. 0 0 

November 4(d) O(e) l(d) O(e) 0 0 

December 2(4) O(e) 0 0 0 

January O(d) O(e) 0 0 

February 1(4) O(e) 0 0 

Ka_i,t~h o(u o.<•J 0 O_ 

Total 1~(4) IJ(e) ~ 2(e) l 1 2 ~ l 4 0 0 0 0 0 0 0 0 

39(4) 28(e) 2~ 22(e) 9 7 16 81 8 89 70 26 10 10 20 60 13 1; 

Attacks 7ielding 3 or more sinkings. (d) Sea Note (4) to !able 2 of Annex 3. 

..i\ttacks J'ielding 1-2 sinkings. (e) Sea l\Tote (e) to Tabla 2 of Annex 3 • 

Attacks 7i0lding a.t least one einld~. 

:i!iote: Only those attacks yielding Rt least one sinkiJJB are considered. 
'i'OP SSGM'i' 9J:• t) ~F ;.t.D.w~~~~~22'11 52 r ~ n CK -

SEQ~RIN INFORMATION- .~.nmx '1 .. 3 .AttLE I 

DECRY.P'l1IONS ON INDIVIOOAL U-BOATS 

u- Date of Date of Dela7 S.n Daya Attack 

Boat Message Position DeO'l!'JP-6 in ······-

ment . or Rff... ttcm Pe!'ii - .... U-43 20/? 20/., 9 eta. 0 

23/7 23/7 18 0 

31/7 s11~1 a/e ... u-56 l 4 l) 

1/8 l/_8 l 1 

4/S 4/S l~ 0 

6/8 6/8 8 0 

B/B e/s 14 0 

10/8 10"/!l ., \ 0 

10/8 10/S 9 0 

14/6 14/8 5 0 

rf/a 17/8 4 0 

U-57 2°1J/_6 29/_6 14 0 

24/V 28/7 ll. a 

U-8·1 18/6 20/6 5 2 

3/8 3/8 13 0 

14/8 18/8 5 4 

18/S 19/S 3 1 24/8 

U-86 18/8 no lnf'i.:: 0 0 ~O/P. Mo tnto 0 0 

1-92 26/S l/6 1.2 Ct 

8/6 8/6 3 2 

ol-: 9/6 4 1 ..... ' !- ., ·•· I/ C.- J.CJ.'b .. U-107 4/S 4/8 12 0 

oU-11'1 21/'/ 2'7/"'7 ·6 0 

50/7 l/8 2 4 

1/8 1/8 1 l . 

U0 llS 13/5 R/6 ;1 , .. 12/6 A 

9/6 9/6 2 0 

l0/6 10/6 ~ 0 

:r.J/6 11/5 4 c 

*!~ one ... ao7 al'ter p~r1od ot peril expired .. 
!OP SIGRB! 9f 0 1' ~F . ~ );~p.!l~~- :r. \::; It:"' )22?1-~2 

St~IJJ INFORMAfiOt~i •I 

TAPJ.:f~ ( c,optinu.ed) 

u- Date of Date of DelaJ in DaJll Attack AaseaaP,.os·l; ~~P.3S3J:?;6 Poaitio~1 D8Cl'JP ... in ment 

o:• Rl~t ti on Peril _ ..... lA:' ... _=:"'_• ~-..._,.,...- ......... _,_.Ill'\~·· 

-- U-l.~i5 8/9 8/S 5 dao .o 

u~1.:;~.; 29/rf, S/8 6 4 

18/6 2'7/6 5 9 

U-129 10/8 10/0 11 ·o 

14/8 l4Za 5 0 

17/8 l9Zs ' 2 

20/S 20/S •4 l 

u-134 21/.6 21/6 13 0 

15/S No Into• ' 0 

U-1:55 18/6 18/6 4 1 

22/6 22/G & O· 

u-154 29/5 3/6 ~ 6 4 

18/6 27/6 ·5 9 

U-155 18/7 16/7 '.LU Q 

u .. 1sn 18/7 19/? 12 0 

U-161 14/8 14/8 J.J. :; 

U-168 \, lJ/.7 15/_7 5 v 

18/7 lB/7 ·'J.11 0 

u ... 1?0 lES/6 16/.6 6 0 

18/6 20Ze 5 2 

2i/6 21/6 i~ 0 

6/9 9/9 5 3 

l.4/9 14/9 3 0 

u .. 112 11/6 11/.6 4 1 

12/6 12/6 2 1 

3/8 3/8 13 0 

19/8 19/8 2 ·3 

24/8 26/8 3 4 

.tJ ... 180 ~/,6 P.i/.6 3 2 

i3/b 9/5 4 l 

u .. 1a3 18/7 24/7 12 0 

PRIC-•SS-3'6 

i'6P S'B0HB1! 4o)•2 ~- TOP SECRET 
iaf HCRE!i' -1,fIDW:F );n.;.A~~°E~)22'11~&2 SECUBITY INFOR · N ~ n c K 

Aimo: 4o3 1 

TABLE I (con~inued) 

-- u- Dato or Date ot Dela7 in DnfS Attack Aaaeaa4' 

Boat ?4essage :Position . Deoryp- ln men15 

- • o.r R/V t1on Pe!'il 

U-185 18/6 16/G 6 da. 0 

3/8 3/8 13 0 

19/S 19/8 2 3 24/S A 

24/8 26/S 3 0 

0'-188 17/7 1'7/7 13 0 

18/7 24/7 12 0 

U·l90 6/8 6/8 B 0 

U-193 26/6 26/6 .., ·O 

u-19a 13/9 13/9 ·$ 0 

u-211 24/5 1/6 l 5 

26/.6 1/6 ··1e 0 2~/6 26/6 . "I t) 

u-214 a/s 8/6 ·8 2 

9/6 9/6 ·4 l 

17/6 17/6 ti 0 

25/S 25/6 12 0 

13/9 13/9 ·s 0 

U•2r7 24/..5 1/6 1 4 5/6 

26/5 i/6 12 G 

u .. 221 24/5 1/6 l. s 

26 15 1/.6 12 0 ·2~/6 22zs 4 l 

26/6 26/6 ., a 

tr-228 24'/5 l/6 1 ;~ 4/& B 

26/5 1/6 12 0 

26/6 26/6 7 c 

U•230 10/8 10/e 11 '.) 

14/8 14/a 5 o· 

19/S 19/8 P. 3 

20/8. 20/8 10 c;, 

'fOf SECHE'f 4o)•~:J 

PRllC-NSS-JG6 T 0 P S E C R E T CANOE 
mnv ~~ W:F ~D,:.Ap.:;~~ IN fi&,w r; tit: )22'11"'62 

TA~LE ~ (continuedl 

U• Date o-r Date of Dela7 1n Dara Attack Assea1• 

Boat Messa"ge ·.Pos i tiOl'l DGCX''JP•• in nient .·.r. 

..E,.r ft!v;. t1on Per11 - - • 

U·232 24/.5 1'6 l cla. 6 

26/.5 l/6 12 0 

26/6 26/6 '1 0 

u-2sr1 19/S 19/.6 13 0 

3/.B 3/8 13 0 

19/8 19/a a 3 

U-'262 3f>/? 50/'1 i 3 

4~ 4/8 12 0 

9/S 9/.8 .ii 0 

10/S 10'/.8 a ·0 

16/8 is Zs 4 :1 

lS/8 18/8 ·s 2 

u-s·os lS/.6 20/.6 6 a 

30/"1 1/S 2 e 

U-333 . lJ/6 9/6 4 l 

18/6 18/5 lg 0 

3/9 3/8 0 

6/8 6/S 8 0 

14/8 14/8 5 0 

U-33G 24/5 1/.6 1 tt 

26/5 1/6 12 0 

2eJa 26/6 "I 0 

U-340. .. '24/7 24/7 ll (1 

U-358 18/.6 n.a/a s 0 

a1zs 21/6 13 0 

19/8 19/S 2 ' . U-S'i'3 19/'1 19/7 10 0 

25/7 25/7 10 0 

26/7 26/7 7 u 

2r'f/'7 .. 27/7 6 0 

31/7 ·3l/7 l 4 

5/S s/a 9 c . u-as2 20/6 ~0/6 l'.f: 0 

25/6 25/6 y 0 

IPQ:P S;!!;Qm;t! 4.3 .. 4 PRNC-NSS-3Q6 

TOP S E CR E TcANOE 
S • llBell!'! 9i1 e -

~F~~~~ ~ r; '-' I\. Ul i221w2 

EQJ1BII% INF0~1JDN , . 

;:·.;.:.!...:':-'..:..... .. ';';... .. ' cont1na~J 

u- Date of :},~'/'" .,I cf' :i.:elay in Da-p Attack Aaaesa• 

Boat Message : 1

nP1 :L i;1~0!:! !)ecryp- in ment 

1.>:i:: H.£.V i; J. (Jll Peril --- ~.I , .. .,..w~.-; "'"°~-, •cm'!'"'r.7!h'l~l 

U-406 23/8 23/8 4da'"' l 

U-413 27/5 27/5 10 0 

u ... 1t1s 19/6 19/6 13 0 

21/6 21/6 l3 0 

14/B 14/8 5 0 

19/8 19/S a 3· 

u ... 435 24~ 1/6 1 5 

26/5. 1/.8 18 0 

26/6 26/6 1 0 

u .. 445 18/9 No Into. 8 0 

u--:.ss ll/6 ll/6 ' l 

19/6 19/6 4 l 

u .... 450 28/5 26/5 10 0 

8/6 8/6 3 2 

9/6 9/6 4 l 

10/6 10/6 3 1 

17/6 17/6 0 () 

8/9 8/9 6 0 

u .. 466 3/8 3/8 13 0 

U-48'7 2:3/6 23/6 13 0 

es/a 25/6 s 0 

u-4aa 11/6 ll/6 4 l 

15/6 15/6 ? 0 

18/6 19/6 5 0 

21/6 21/6 13 0 

u ... sos 9/6 9/S .. 

... 1 

18/6 18/6 5 0 

3/8 3/8 l:S 0 

19/S 19/8 2 3 

U-·510 9/B 9/6 4 l 

3/8 3/9 13 0 

14/8 14/,a 6 .o 

(J-51& d/.6 llo lni'o 3 0 

S/9 6/9 5 0 

!OP SESRS.' lul•S PRNC-NSS-346 T 0 P S E C R E T CANOE 
!£ .J\EF ,lO.:.A,?:>~5~~ steemt.Y w F0 :- 8 t" ~ :I! t 1't :I! UI )2291-62 

ANNEX 4. 1 1tMATION ' ~~~_g;_J,,,~l2R.nt1nu.edl 

u- :,)r;: \ :·. .,}~· .. .if:r1 ·~: ·~ r:.J Oela7 iu Da79 Attack A1se•1-

Boat ~':1'!.:. ... =-=.~,~~i.l ~~-<~s;. ~1 on Def}rJpt1 O~l in ... t 

~ - .,..,._ • N•1,• • OJ.' H/V .... ..__ .......... .. _ Pei-11 

- - • .;:: ... • - .W'l.!'"4.- ;t,;.r_ :· IT 

U-516 1£! 1~1 24l7 12 da .. 0 ~&/'? Wo 1m·o 7 0 

15/8 No Info 4 0 

u ... s1a 27/8 27/6 9 0 

u ... s2s 10/8 10/B 11 0 

Uw52'7 l"lb 1'7/'7 .13 0 

lBZ7 iaZ7 11 0 

24/"1 24/'7 11 0 

u-.530 ll/6 ll/6 4 .1 

'0'·~532 1st.r1 15f 6 0 

18/'7 24 ., 18 0 

26/7 No Into r, 0 

u .... 533 18/.7 24/V 12 b 

26/7 Ho Info '1 {) 

u . .,535 15/.6 J.0/6 ., i 

lB/6 20/6 5 2 

r.r ... 535 18/6 20/ES b ~ 

21/6 21/.6 13 .o 

8/.9 az9 e 0 

9/9 9/9 !5 . s 

u-ss2 30/.5 30/5 6 0 

3l./5 31/5 G 0 

u ... sse 24/.5 l/.6 l s 

26/5 iZ& 12 0 

26/6 26/6 ,., 0 

u ... sse 13/7 13/'1 13 0 

16/7 16/7 14 0 

u .. 559 24/5 1/,.6 5 0 

26/5 1/6 12 D 

u-571 15/6 18/.6 v 1 

:sza 3"/8 13 0 

14/8 14/8 5 0 

PRllC-ISS-306 

T 0 P S E C R E T CANOE 
di w;:F ); . 

sEdi!fjNfMl@I~ ~ n __ '"' ~ )2271-02 

!!'f1!:!LL!...n9!Jt1u~1.!,.il 

u .. Date ~t . · ·Dat.e · ut Dela7 in :oars Attack A1aeasBoat ~essage. ·Position· DeOrJP-· in ment 

- __ ... . ~r.Jtl.! ..... t1on Peril 

I 

lJ'-572 I 

l.l/6 ll/6 . 4 da' ·· • CJ 1 

23/6 23zs '.3:. ' 2 

25/S · 29/6 . , 14. 0 

3/8:. . . 3/8. ' · 13 0 J.sia · .. ' 

tt-590 18/6 ·. · .. .. , l 

1'7/6 1'7/8 6 0 

u .... ss1 Jf 11 0 

u ... 592 8/8 .8/8 :I a 

'0'•699 1'11 0 

11..SOO 15/.8 16,f ., 0 1eza 19~8 lS 0 el.Zs. 21 6 '18 0 

esze eaze ' 0 3/e · aze lS 0 

14/8 14/.8 & 0 . 'Jll/8 l''i/8 4 1 

u-eos 24/:S J./..6 . 1· & 4/G •G 

aeze J:/.6 , .. 0 

287• 26/6 0 

u-eot 1'11 0 

v-soe "24/.S 1/.6 1 I 

eszs . 1Ze 18 0 d6/8 2~l6 ' 0 

11-613 17/7 17/7 18 Q 

11•616 18/.6 16/6 '1 0 i9Zs 19/6 lS 0 

2.i/.6 2i/6 13 0 

' 18/B 1'o·Into ·a 0 

U'-818 . 15/6 18~6 ,,, 1 

aza s e lS ·o 14Ze 14Za & 0 l'f/e . 1.,/8 '· 1 

'0'·621 6/9 'e.le -5 o· 

14Z9 14/S s I 

15/9 lei/9 ~ .1 

!OP SESRI! 4·)-7 '• 

PlllC-ISS-JH TOP ·s E CR E TckMOE 
. ..~. ~ ~ ~6.¥~. ._ . 

TOP s1cne ..i o~ ti:l .n ·\.J .n. E ~U>>ee':w1 

SECU;Rll)' INFORMAIIOff. ., _ ,, .. ,-, . --:,: ._·; : :· . 

u-

~oat 

-

U-634 

U·64l 

u-642 

U-645 

tr-648. 

\ • . 

U-662 

U-664 

U-666 

11-709 

0'-732 

u-75'1° 

. ·,. :;:ABIE _ _I_..(.22B~inued)::·fj•/.'. ·~· ..... . • ·, ·.. I • ·. it f • ,•":. '. • .. !•'"'• • ...... • 

DRte ~,'!.-. · nirc.e 'lf .. Del~J'' in· .-DM:,ra . •/Attack 

Ma f! s.~e:~ · P·c1;1 i ti a.a. . Oe~ryp- . :. ; i;.'l . ·· : ::-. · .. 

: or: R/v · • '. · tt:lol.I·. · " · · P6ril · . · • ......,.. ... "ftlll,AC'llli(,'lftl ~-.. 'fll"llll•r....;;..... • .......... ........ ~ --------

18/6 . la/6° . ·.·:·: .~: s:~·dac,.· ..... ·o ·, . ·. : ... 19/G · · 1~za.: . · : ·~· · 13 · . . ~,. · · o · : ·. 

21/a · . · · 21Zo(': .. · ..... ia· ,~-: .·· ~~t; _·.-.a.;~' . : · 

15/a · . is/"/8:.1 ·.~ -~ : ,,:.; ., \ :":.: .r:::.::..~ ·· o: 

19: 'a · · l" e , · · · ·

4 : ••• 2 ·A ..... • •• • 3 '- · .. ··20-p:ta~ ·~·. '·.>..;; ;·~.-~ .. ·· ~::· · :; .... :.- · l 20/.8 . , . 7~ .. . . • . • . ,... ... . . . .. so/a · ·· .:. "2ri/a .. · ·~;~...- :'.~.::10 . · o 

24/5 ii.a .· ;. ·' : l s 

26/5 1/6, . 12 0 

26/6 26/6· .,, 0 

24/j; 1/6 1 5 

26/5 1/.6 12 0 

26/6 26/6 ? 0 

' 

2/9 2/9 4 1 . 8/9 8/9 8 0 

17/7 17/.7 13 

18/7 lbZV · 12 

24/? . . 24/"/ 11 

25/7 25/''1 10 

i~~e 1si.s s 

2.LJ.6 21/8 18 

3/G 3/..8 13 

14/8 14/.8 5 

19/8 19/8 2 

lf1l 

30/7 

4/.B 

9/8 

18/B 

24/5 

26/5 

26/6 

8/.9 

14/9 

13/'r/ 

18/6 

N11 

30/7 

4/8 . Sunk 9/8 

18/8 

1/..6 iza 

26/6 

8/9 

14/9 

13/7 

·ao/s 

0 

2 

12 

13 

3 

·1 

12 

7 

6 

4 

. 13 

5 

.0 

0 

0 

~ 

0 

0 

0 

0 

3 

0 

3 

0 

0 

0 

5 

0 

O· 

0 

0 

0 

s 

0 

4/6 

.. 

'lOP S"gCJiliT T ·O. ~ ~S:J CR ~ T CANOE- . ~· 

Aaseaa-

·ment 
'1'9f BEf'!tET ~tffi -~F ~W ~ SECUR~ INFOR~'f ~ u ~ n 

0)2271-52 

TAPLE I 'continuadl 

u .. Date of. Date of . Dela7 1n Days Attack AaaeasBoat Mesa age . ",Position . Dec:ryp ... ~ .in men\ •: 01' P. 1v ' . ti on Peril -- _......._.....~3.:-=.aA.S'ln • .-.-...... ~ ... .!le .......... ~--........._. 

U-758 e/6 a/s 3 da~ · · ·. ~, . 

9/6 . . c;; - • 

S/6 2·' .1 

9/6 . f:/6 4 •. 0 

10/6 10/6 z . l 

r1/s 17/5 5 - 0 

10/6 ·18/6 ·. 5 0 

6/9 ... 6/9 5 0 

8/9 :·· 8/.9 .. : .- ·. 4 1 

13/9 13/9 $ 0 

14/9 14/9 3 0 

tr-759 11/6 11/6 4 l 

U-760 ao/7 30/7 2 8 

4/8 4/9 12 0 

6/8 aza e 0 

9/_e 9/S s 0 

10/8 10/8 e 0 

·10/s 10/8 ., 0 

13/6 13/8 i 0 

14/8 14/6 - 0 i') 

16/8 19/8 $ 2 

TJ-~47 14/8 16/.9 . s 2 

18/S 1aia 3 2 

19/8 19/B 2 l 

24/8 Sunk 2.,/8 ! -1 27/S. .. 'B 

ti'-951 24/5 1/6 1 5 

?.6/5 1/6 12 0 

S/6 8/.6 s 2 

26/6 '.26/6 ., 0 

U-953 24/5 1/6 l 6 

26/5 1/6 12 0 

26/6 26/6 7 0 

'f6P S'BCffift 
T'l'ABLF! Il 

!!!!:~ ~ .. l U...P..CAT HEfUET.LINC f!}~J:T oMi.m<W_.._...._~-··~IM-W 

U-Boat Month ot ;;!!araet,er of Allied Uecrypt;1on •Num=ibe.....,r ____ 'fte ____ ..,r_ir_, a_t....,..OJ?..,el'_a_U_on___ _._,_~_unk _______ u.i_g~lliaenca 

U•ll6 X-8 Sprin& 19"2 

u-111· ·· 1-B October 1942 

·r • • • 

'• 

U-ll.8 X-B _ . ., sept.. 1942 

' . t • ... -: • '":• ·: ... : .... 

·- . 

u-ll9 X··S. Feb... 1943 

X-·B Oct., 1943 

sept. ... 194.3 

Not. known.. Proba· 

ably Oct.o l9lt2 

? AUJt.< .194.)" 

40<4'; JSCW 

en: it./C 

12 June 1943 

JlOff, Jl+oW 

CVE A/C 

21+ June l 943 

45CW.t i;l~ 

Surtace Sh1pa 

Act.1ve o!lt. ~nd 

ot war, 

28 October 1943 

490ff, )JO(f 

CVE A/C 

r:tone~ rlefore decryption began 

t"unct.ioning o 

r..ood,, Two m:Bssages invol Ying U-l 17:. 

t,ranemit.t.ed 7 days before the att.ack., 

were <16cr;ypt.ed tfithin 2 days ... (See 

~ection 4 .. 3 .. 1,.J (Sailed 22/? from 

80l'deaux,, J 

Veey good .. M.esee.gea giving her poei t .. ton 

tor 8-9 Jur• were deeeypf'Ad ll Jww ...... t,ne 

day ~fore the at.t.scJc ·.(See 8er.t.ion 4~ )el .. ) 

Of' doubtl'ul valueJ 18/6 message ( deo:eypted 

J.'J,6) gave probable rendezvous position at ~ Rt1 .)2°w tor 21/6. Known to be rfJt,,urning., 

~:hmk in Bi&C&..T" 

Veey good. 26/10 ( dec:eypt.ed 27 /10) ! no 

~oaition. Mentions discontinuing Je"<rti~ 

llv!\ing because ot hea'VJ' eea.. 26/lO 

(clecr.;·='ted 27/10) gives his position~ a11ya 

ho is le&:<rlng square tor 2 d.aya. 27/10 at 

llOSA (decr,y~-t~ed 1815/27Z) BdU orders refuelling rende~,·"'na. (Aleo a message rrom 

BdU giving n/V to1· ~-488 at 37°N. ,43oW-. 

'Z1 /l0-2042 (decrypt.ea :~150/27) orders 2 

U-Boats to refuel from. U·-?20., 

"' .. 

"I' 

.. 

~ I 

l;! 

ti: 
Atm;X 4o3 TABU:: II (oant.inued} 

u-.Boat »onth of eharact.er ot Allied Decryption 

!umber ilR! ... ilii'at 91!£at1on Sunk IntellJjjenqe, I I N a - I •a Iii m T 

W\ U-i2J3 X-B liq 1941. S Juq 1944. ?ofo' msaagea tound referring to u ... 233 tor .... • 

C"-- 420Jt. 6Qq¥ .. 10 daJ• pravioua to attack .. 

"' surtace $1ps. N 

U-2.34 X-B April l94S Active Nil .. 

U-459 XlV' April 1942 :u. JuJ.7 .19/J. tto mention 1n meesagea, ea.t.ward ~• .. .iocr. paeeage.. Sail.Gd 22'1 trom 

landba!Secl A/C Bordeawto 

U-460 lIV July 1942 4 Oct,ober 194.3 No deceypt-ed meaeage until 4/lO 

43Cl;t .. 29.-. (deceypt.od 10/10) ordering 

CVE A/C relidezvws poaition. 

u-461 XIV June 1"942 - 30 Ju17 -llJ43 Hot.'2ing until report o~ at.tack on 46~ .. llOff .. 30/7. Olltward paaeage o Sailed 

Lancibe.sed A/C '11/7 trom Bordaauxo 

XIV September l 9lt2 30 Jui,. 1943. Nothing until report. of attack cm. 

450R. llCUI. 3on ~ rutwiu.·d j>aaaago.. Sailed 

Landbased A/C. 27/7 tram Bordee.u..'!t .. 

•./+63 XIV Auaist 1942 l.5 Uay 194.3., Sailed 1"1~0111 Bordeaux 12 1lay 1943; 

45q; G lOOW" sunk in B1ecq ... ·· No mention in 

Landbaaed A/Co mesaagee., 

.. nv Auguat; 1942 20 August 19~ Nil ... 6lON. 14CWa 

LandbaG$d A/C 

-"137 XIV :Uarch 1943 JJ July 194-3 Not good:. Messages <.ln 23/6 (decrypted 

3l0N .. 34°Wo 6/7) and 2S/6 (dooryptf.td J/7) gave 

CVE A/C poaitiono Sunk l8 days att~r latter 

meesaieo ¥ 

II: 
ANDJ 4 .. 3. 

N V•Baat. llOllUl ot 

II\ 

D ..... .:&re . rue' 9ft~t.iml 

(::! O...t,88 m ·11q19u N 

C\I 

-

s 

U-1,69 XIV J"17 194' 

U-490 XIV lfq 1944 

TAU II (contiau.ed) 

Sunk •W ,. ,,2heraoter -gt AUied De!!'fltitm M!YJl!r!! 

26 April 1944 vv., gaodto ... ace 20/4 (dec17P\9d ... 18"119 380ft., dq) gave 22/4 rendeaYOUa po.tt.icm. Starfaee ShipJ .. 22/4 •asage decqptecl um dq eave ,.. .. poelU.on .. 

8 Aupat, 1943 ~ lt"t. a.UO.d 1n measagea .. Sailed a/? 62•· ucw~ tram liel.1 Ot&twerd bour&du 

Landbaeed A/C. 

U. June 1944 Oc.'Ud., · Jreaaage ot 10 June• dec171>tod ltl°N. 40oW .. the 1ru..-. dq, gave polition{f Cft:.A/C and Slu'~oe Sbipf 

.. 

.. 

"i' 

., 

l:1 

I 

l;1 

IE