Bonito, Trumpeter, Narwhal, Sucker, Bloater, Catfish and Bounce all appeared. (2) Bombe time became very much more plentiful, particularly on the 4 wheelers. The following table shows the position at various times
| 3 wheel | 4 wheel | ||
| Dec. | 1941 | 12 | - |
| " | 1942 | 40 | - |
| June | 1943 | 72 | 4 |
| Dec. | 1943 | 87 | 95 |
| Dec. | 1944 | 152 | 160 |
| May | 1945 | 152 | 180 |
(3) Straight cribbing played a major part in breaking. We could afford the bombe time to run all W.O. cribs on Dolphin and Shark and on the latter the short signal cribs greatly deteriorated while the R.E's became very good. Except for Porpoise and those of the new keys which also used the throw on system we relied entirely on cribbing - and in due course Porpoise and almost all the other throw-on systems abandoned this method of indication.
(4) All this meant a tremendous increase in the importance of cribbing in relation to other cryptographic methods. The running of all W.O. cribs killed Banburismus in the course of a few months and the reasons for two separate sets of cryptographers disappeared. Cribbing is an extremely economical method so far as skilled staffs go, so from now on we shall see a steady and fairly rapid reduction in cryptographers and the absorption of all cryptography by the crib room.
The American Contribution.
5. Just about this time the help given by Op. 20 G began to be a major factor in our affairs. This help was of two kinds (1) Bombe production (2) Cryptographic work.
6. To see the effort made by Op. 20 G on the production of 4 wheel bombes it is only necessary to look at the figures. In the last half of
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