ARMED FORCES SECURITY AGENCY 

From: AFSA-lJ:. 

To: oor l • •• • w 

W./50/TCRS"ID/AFSA=-14 

Copy Noo 3J 

Declassified and approved for release by NSA on 05-23-2014 pursuantto E.O. 1352a 

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DF 21<rA lll/50/TOPSEC/ AFSh·J 4 

COHVOY TRAFFIC OF THE ALI.IFS lll WORLD WAR II 

AND THE GERVAN N~VAL INTERCEPT SERVICE 

1. The attached is an Arm.ad Forcss Security Agency translation of 

an article by Wo F o Flioke entitled: "Dei• Geleit,zugfUF...kV'erkem' der 

Alliiarten im 2o VVel.tkrieg und der deuteche llarL"l.e=Hoi~chdiensto 11 Th0 

original was transmitted along with several ot.her items through t.lie 

Chier~ ArJl\Y Security Agency fran the Chief'~ .ASA Europe by letter) subject: 

"Material. by Wilhelm Flicken dated 12 So.ptcmber 1950 a.ri.d is held by AFSA--14 ... 

2o Contributions b;r Flicke pri<>l. .. to August 1950 have been issued in 

parts under the general short ti"CJ.e: DF 1160 i'hose received after the 

publication of the list of T:;EC<l! tra11slations DF 210 w,ill be g:-ouped 

under the number DF 219 and tho parts designated as before by letters., 

An aarlier pape1~ on the Gorman Maval Intercept Service was issu_ed e.s . DF 116-Xo 

October 1950 

Translated.: R.t"l.Po 

Distribution: ?formal. 

2 

35 copies 

8 pages 

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DF 219-A 

CONVOY TRAFFIC OF THE ALLIF.8 IN ~roRID Wi\R II 

AND THE GERM/iN NAVAL IUTh1WEPT SERVICE 

The Weaknesses and Daf'ecta or 

the Allied CO."'lVOY Trai'fia 

Lessons for the Presant and the Future 

Naval Intercept. Servfoe and Rad.cu• 

By W:f.lhelm Flicke 

The Intercept Se1"Vice of the German Navy (B=Dionst) ple.yed no loss a 

i .. ole in World War II than the Intercopt Service of the other branches of 

the Armed Forces. It provided its Command with i.'1.forznation uh:tch could 

have been decisive in naval 1tarfare it th9 German Navy had had at its 

disposal a sufficient nu~her of ships and especially of submarines~ 

Ha11y details of the pra.ct:tcil t"Jork of the Na.val Intercept. Service are 

not m:traly interesting a11d noteworttiy but al.so instl"uct.ive o Espeoial.]3 

so is the chapte1• on 1~he 11'.onitoring of Allied (!onvoy ti~a.f'f'ic., 

This chapter appears all tho more sign:i.ficr.nt today when the general 

TK>rld situation brings the employ1~0..11t of convoys :into the realm of ponsibllity 

or even probability cnce more. Parallels to World liar II result which merit 

increased attention because today the situ.at.ion appears et.ill more serious: 

tha powe1• r.hich appears as potont.ial opponont or Allied convoys has at its 

disposal mans . na.bling it to rr:.ake bettol" use of the. i .. esults of the intercept 

service than the· German Navy couldo 

In assessing the work of the German Na.val Intercept Servica it ia usually 

assumed that the direction finding service played the decisive role. This, 

however, was not the ca-.seo The m.l.val !ntercapt Service did,, to be su!"e, have 

at its dieposaJ. a v:hol'3 network of very good dil•ection fir:-ding establishn:entso 

Many beariri.gs were taken. But if we regard this co:nplex from the standpoiut of 

its usefulnesa for the conduct of l'laval wa:-fare, then l·.e find o!'lly meagre results .. 

Operationally tho i;aval Direction Finding Servfoo played no great roleo 

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wa must. it is true. mention one exception here: at the beginnmg or 

the war the English end French naval forces in the ?Jorth Sea radiood around 

a great deal so that the movements ot these n.eet units could be .follmied 

readilFo With the begmnmg of the campaign in the -r:est this ceased to be 

the case and the situation did not recuro 

_. _ _...._cm 

The decisive source fran which the Ger-man Naval Intercept Service drew 

its inf'ormation during the entire war was the field of c:eyptar.alysis and 

trai'!ic an&lysiso And these lines ot endeavor rou.rid t.heir bro~.dest i'ield of 

activity in connection Ylith the convoy traf'fico 

:rpo ci2hei: (cryptographic) si.stems se:r'V'ed as ba.ais for German cryp'vanalytic work in this direction.. The mo was called by the Germans "Verfahren 

------- Koln".. It ''as a cipher system or the l!ilglish Navy and its proper deeignation -

nevei .. becam lmown to USo Tho system was solved analytically in Berlin.. From 

the nussages which were enciphered in this system. and decrypted by us the 

distribut.ion ot the E.."lgl.ish t1eet could be recognized currently in very 

complete manner~ 

The second cipher system~ which 1•as also solved by analysis, was termed by 

us "Verf'ahrei1 Franki"urt." In this case a common Englieh=American cipher system 

r1as involved "Which appeared after America's entry into the waro It was introduced 

to take care or the radio trai'tio between &gland end Amsrica~ or betv1een 

English and Amarican of.fices (stations), which was necessary in connection with 

the convoy system. It was a ,.ad.igit code which 17as enciphered l1ith an additive 

scquencoo 

Both systems .... "I\8111" and 41Frankfurt" , could be docS.phered at all times 

domi to about the midd1e of 194lh Later the "Frankfurt" system \Va.s complicated 

through the fact 1'hat a general, consecutively used (,9.V;,r,g1l~~.~-!.!!-!1!.~) additive 

sequence was no longer used for cncipho1•ment ~ but instead the additive which 

i'la.s found was used only tor 2lli'. messageo For encl}Jh6r."!lent there was a 1•hol.e 

book Of "individual u.ddit:be aequoncosn o 

From mid 1944 on this mde deciphermsnt tar more difficult; consequently 

from this fX)int on decodes tJere l"arel7 t:Lr.ely, they always limped along beh:ll1d.o 

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From late l 944 on it was no longer possible to decipher messages 

in this s7stemo 

--.. -.. Already at the beginning or the war (l 9'39) the Crypt.~.nalytic Service 

ot the German Navy was in e. position to .follow Ene.1ish convoys quite wello 

Hence ine can state that from the f'all o:t 1939 to mid 1944 the Cryptanalytic 

SOI"V'ice was able to i\irnish the Naval Comrna..'ld all the data necessary- far 

combatting convoys. 

The. tragic f ea.tura - it wa may call it thus .... lay in the fact tli.at, 

'Rhile all convoys could bo clearly identi:t'.'ied,,, they could not be attacked 

dus to lack of submari.l'JiJe. 

Ths German N'a-ll'al Crypt.ana1ytic Service a cored one 0£ its greatest 

S'l.l.ccesses in the spring of 1942 when a convoy of 9 ships on the \'lay from 

Tr:inidad to England could be wiped out completely on tlle basis of decrypted 

radiogramso 

-..... -- The weakness of the convoy traffio of the Allies lay in the system which 

waa usod continuously and almost without changeo Thi.a izoint cannot be otreaaed 

too emphatically~ because under tha conditions cf today and tomorrow on0 must 

count on a repotition or those mistakes. Ir at that time the West.ern Allies 

had raced an opponent who could hav(!) cormt/i;ed a much stronger .force of 

su't:!llat•i?lea~ then no convoy would ever have reached its desi..ina.tiono 

The first mistake lay in the fact tha.t the socalled convoy radiograms 

were transmitted by two £i:i-.-ed stations (which were al.W23"S the sa.m),. So far 

as I recall,, these were Hali£a.x fw the USA and a station near Bristol in 

The second mistake l~ i."l the f'act that the convoy 1•adiograo \1ore so 

characteristic in their outward. f'm ... m1 that they could be cleP.rly racognized 

as such evon be.fore decryption. Incidental:cy it may be .msntioned that e"'ren 

after doeryption became impoasiblo (1944) it v1as possible wlthout .further ado 

to get first rate clues rrom the )It;qe9rze:teg, radiograrii..so Thj.s assertion -

which may eotmd incredibJ.e - bringa us to the third m:.l.stako me.de by the ,,,.llieso 

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The structure ot tm convo7 messae;es was stereotype and f:i.:xed. Short 

letter goups were used for designating the convoys; these designated thct 

date and time or sailing,, port ot destination, composition ot tho convoy# 

number ot ships• nuni>oi .. of' the routes,, distance between ships, a.'l'ld i~oute 

expressed in degrees of longitude and latitude,, cargo~ escort forces, name 

of the commodore,, assembly points !01• stragglers,,. etc. Woi~st of all was 

the serial number of the CCllVOYo 

Interpretation of the group a was usually quite simple. Thus BX signified 

Hali.tax.,, SC - Sydney Canada., OG - outwai~d Gibraltar,, Hl - homeward Gibralta.ro 

These letter groups gav" in£ormation regarding the port of daparture and 

port of destination. But they revealed. still more. If' the group ON (outward 

North Atlantic was transmitted, that gavo at the same time tho spocd,. i.e o 

the normal speed or a.bout a.5 na1ttical miles. On the other hand if the group 

a1S (outward North Atlantic SJ.ow) appeared,, then a slow convoy with a spaed or 

about 7 nautical miles was involvedo 

CB meant outward South Atlantic, i.e. with speed of 805 !mots. SL ... 

Sier1•a Leone to England with norm.i:.11 spaedo SLF - Sierra Leone Fast, l.oeo 

with speed or 9.5 knots. UGF =United States Gibra1tar Fast,,. while the 

reveroe route was GUF .... Gibraltar United States Fasto 

In thia situation ono could always calculate the e:l::.a.ct location ot the 

convoy and impart it to the lurking submarine packs .. 

or oxceptional importance in this connection wore the social.led assembly 

points; these were fixed and radioed in order to give stragglers (those which 

had fallen behind due to eng.ino trouble etco) a chanco to join the convoy by 

the shortost route. From a knowledge of the appointed assew.bly points one 

could deduce where the convoy "Kould pass tu:1d: _that .made possible the commitment 

of submarines. 

The fourth weak point in the convoy tra!'.fic lay in tho rhythm of tho 

" convo:vs1 this was so clearly l•ecognizable that ono was in a positi011 to 

calculate for \Yeeka in advance the days on which convoy Nro X would put out 

to seao 

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This was facilitated by the .fifth weak point in the Allied convoy traffic, 

namely the radio traffic which i .. egule.rly appeared during the assembly o.r the 

comroys and which could be recognized just by tha 5-letter groups or the radio 

names (call. signs} and attorded clue.so It \'JD.a possible to dra\' from th0 radio 

names the reJ.iebl.e inference that a convoy 'Was being gotten together and ~nhere 

it was heading (trom the convo7 rhythm) a 

These secondary characteristics remained throughout the entire war and 

were helpful,. evon after the change or ciphero The Cryptanalytic Service of 

the German Navy in conjunction with the Ei'al uat ion SerV"ice had become so well 

schooled th.at the radiograms which appem•ed were "rsada.ble" to a certtd.n extent 

without having to decrypt themo For instance=' when a message a:paa.red~ OM 

knew which convo;r it concerned,, \'lhere it was going, whether nslow" <:i'I! "fast" 

or normal,. etco 

Only the situatian had changed meanwhile with the introduction of radar 

oquip»mt on the part of the Al.J.ieaa The bast 1•esults of the Naval Intercept 

Service were no longer of BnJ" useo 

It is not without interest that tho Naval Intercept Service recognized 

very early the 'l!l!e ..... of 1~~~r deyicaa~ by the Allieso About the beginning ot 

1943 it was recognized from the decryption of a aeries or radiosrams that 

t.he enSl!'zy' had at his disposal some means or othar !or tixing hostile sub-

.marines o The messages rrom which this was deduced were enciphored by the 

English-Almrican Convoy Code (which we calJ.ed "Frankfurt rt) a Submarine 

aituation reports were radioed every dey- in this codeo 

Nolt,, however,, it was striki.."lg tha.t the positions o.t the German subnarines 

were suddenly given with astonishing precisiono Moreover the \'ford 11detected" 

kopt coming up in the messages o 'rhat was al1 the more noteworthy because the 

submarines remained under water virtually all the time and sent no radiograms; 

there was only radio traffic within the pack v.hen a boat made contact ivith 

the enenv; there was oomn1.mica.tion 1vith Berlin or with tho f'loti.1.la. chief" only 

on orders i"rora. Berlino (OpeJ:'ational. orders to submarines camo only i'!'om Berlin, 

via \Vilhelmsha.ven, Bordeaux, etoo)o 

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It became especially cl.ear that the enem;r had new technical means or 

spotting subma...'"ines when wo had picked up ccnvoys by our intei .. cept sor-~ice 

and our eubmarines prepared to attack; then a change of route ensued at 

once !I which was prOJJptl.1' recognized by om.. intercept sel"'Vice. 

It could not possibq be a case or enemy decryption; in the first 

ple.cG l.i1e above mentioned reasons argued against this, then~ too,, tho 

fa.ct that the enemy used such terms as 11seen") 11deteoted" Gtc • .> although 

the submarines were under water. 

Tm essence of the new foreign technique and tte method \Jere still unknown.:1 

to be sure1 ~t the fact was established that there \Tas something or other :1n 

existence ror spotting submarines. 

A little later a .British aircraft. was shot down over tha Atlantioo In 

this case we sucaeedod in capturing the English A:ir Ccdeo In this volUJ!lll wo 

fowid tor the first time the expression 11rada.r"; the term "detecM.ng" also 

appeared hereo 

Now it was recalled that oven before the 1var it had been noticed t:hs.t 

the English were instituting experiments with a radio moasuring device, ai..:!. 

indeed tor ehol't distances o There was a peculiar ticking observed on the 

submarines body when a radar beam hit it. Then~ sho1 .. tly before the Wal" one ' I 

had a Zeppelin fly along the English coast; this time, too, it was observed 

that tho airship was mado the object or baariri.gso 

It \Vas a.lso recalled that at that time the English had bought up a 

whole year's production of Brat1n tubeso Now one knew or what type the 1101'1 

dsvico nmst boo 

-........... 

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