Cryptographic History of Work on the German Naval Enigma

4. The decision on run all W.O. cribs on Dolphin was fatal to Banburismus; we did not officially abandon Banburizing until September but such a high proportion of the days came out before Banburismus had got under way that it soon became clear that the expenditure of staff involved in Banburismus was no longer justified.

5. Finally there was the news that a new reflector (Caesar) and fourth wheel (Gamma) were to be introduced in Shark on July 1st. This information (contained in a June Oyster message) was a serious blow to us, though not so bad by any means as it would have been earlier when there were fewer bombes and no 4 wheelers. We knew how to work out the wirings of the new wheel and reflector by the Stecker Knock Out for which all that we needed was a long R.E. and a good deal of patience; both of these commodities were in reasonable supply. The real trouble about the change was that it multiplied the possible number of W.O's - and therefore the bombe time - by four, since any of the four possible reflector/fourth wheel combinations could presumably be used on any day. We had to hope that the enemy would fail in some way to take full advantage of the change; this hope was to be amply fulfilled.


6. In July we duly obtained our long R.E. and broke the wirings of Caesar and Gamma; long afterwards we discovered that the wheels had been captured some time before in North Africa but not sent home on the grounds that we already had plenty of wheels! The breaking of a few July days revealed the gratifying fact that the combination "Caesar Gamma" remained in force for the whole month - we had feared they would vary the combination with each change of key (i.e. use Caesar Beta, Bruno Beta, Bruno Gamma and Caesar Gamma indiscriminately throughout the month). This meant that we should probably spend a good deal of bombe time in making the initial break into each month to determine which combination was in use - and that for the rest of the month things would be just as they always had been.


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