Cryptographic History of Work on the German Naval Enigma

wheel the whole time in which case it was the first of all keys to use the four wheel machine. This break surprised us even more than that on Sunfish - it was universally thought that a version of the unsteckered machine was being used. As Seahorse was as much a Japanese as a German key it was of particular interest to Op. 20 G and they modified some of their machines slightly to make them suitable for running 4 wheel "throw-on" menus; nearly all the later work on this key was done by them and they ultimately succeeded in reading most of the 1944 and 1945 traffic.

10. A major event in September was the abandonment of Banburismus accompanied by a considerable staff reduction. Charlesworth, Good and Wylie all left the section at this time as did 21 girls from the Big Room. Charlesworth joined Twinn's section and Good, who had been responsible for a considerable amount of the most valuable statistical work done in the hut, joined Newman's section (Fish) in which the highly mathematical nature of the problem gave more scope to his great ability in this direction. Wylie, the head of the crib room and deputy head of the hut, also left to join Newman. Except for Turing, no one made a bigger contribution to the success of Hut 8 than Wylie; he was easily the best all-rounder in the section, astonishingly quick and resourceful and contributed a great deal to theory and practice in a number of different directions. This reduction from ten to seven cryptographers seemed fairly drastic, but looking back I do not think that it was drastic enough and we could well have let one and probably two more leave at this time.

11. American four wheel bombes were now coming into action in considerable numbers and it become clear that we were not going to be able to employ them satisfactorily on purely Naval keys. In September, therefore, we started weekly meetings of a committee formed of representatives from Hut 6, (the Section breaking Air and Army Enigma) Hut 8, Naval Section, Hut 3 (the Air/Army intelligence section) and the Op. 20 G liaison officer. At these meeting priorities were allotted to all the keys, irrespective of their service. When cribs were sent to the


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