Enigma procedure (1939)

Introduction

No document tells us that there was a new manual or even a correction to the 1938 manual. However, at the beginning of 1939 the Enigma procedure changed slightly: the group containing the kenngruppe was systematically placed in first position. No doubt the variable position generated too many errors.

Perhaps no changes had taken place in the procedures, but quite simply the location of the group containing the kenngruppe was always indicated in the first position in the key tables.

Messages deciphered by the Allies from January to May 1940 followed this procedure.

We can notice that:
1) Wheels in use since December 1939 included the IV and V wheels.
2) The number of steckers was variable: 7 or 8.

Example of decryption

Here is an example of an key list. It is fictitious. No one from this period have been found.

Geheim - Heer - Maschinenschlüssel für Monat Juli 1939          - N°763
              Kengruppen Einsatzstalle Gruppe: 1
Tag  Walzenlage   Ringstellung Steckerverbindungen      Kenngruppen
 31  III  V    IV    24 20  3  BK CQ HI MX JP NZ AR ST  urh bkf mxs hqe
 30  IV   I    II     8 12 10  NW CQ BO FL DK SZ GX     oeg iyo rnv naj
 29  V    III  I     22  7  5  MS QW HN AU IY OR JV LZ  kep swl lpe ntf
 28  V    IV   III   10  6 19  EH KZ IW NV BT DU GY     ypc zdz zqd rpu
 27  III  II   V     17 19  4  GJ LM DS HP FR EY OT     ytm cwh xvk rhu
 26  II   I    V     24  3 23  HP UX BL IM NO FW DJ AG  ohu nvx tie phj
 25  III  I    IV     7 20 18  OV SX FQ TU GI DL YZ     ujx ycs pxh gyv

1230 – 98 = HIT = GJVCS RDMNZ OOKOB MUOXM QJQNX 
VQHYV FXOBF BVKJZ VFZZJ DJPNX SDDLW MHODX QZLSA 
VMTFN MCUCB JSWOX VTFDE CJKDG XKUZN WFC