The History of Hut Eight

or diagonals like WSX were a strong confirmation that the right alphabets had been found. Pronounceable trigrams like MAR were exceptionally good in N. Africa but there appears to have been elsewhere some sort of security legislation against pronounceables.

Finding alphabets was never very difficult and could normally be completed before midnight of the first day's traffic. The rest of the process was merely a simplified form of Banburismus. The starting position of all messages was known and they were compared at distances appropriate to each wheel order assumption and middle and right hand wheels were confirmed or rejected on the basis of fits and good counts. This was an amusing and quite rapid process: the wheel order was normally reduced to a minimum after a couple of hours work. Depth cribbing was possible but not necessary as the alphabets supplied sufficient material for the bombe.

For long periods during the N. African and early Italian campaigns Porpoise was urgent and a fairly extravagant running policy was pursued. The alphabets were bombed up on 12 machines as soon as they were obtained and the Bombe Hut started to run all wheel orders: then, as the counting progressed, directions were telephoned over as to which wheel orders to run first and which to ignore completely. It would have been more economical to have established the wheel order before procuring the bombes, but this would probably have meant an overall delay of 3 or 4 hours in breaking and this system whereby all the bombes were plugged up and ready to run the right wheel orders was preferred. At times of extreme urgency throw-on menus, which could be started 6-8 hours earlier, were experimented with, but the experiments proved very extravagant and not very profitable. The great success we had at a later stage with Porpoise cribs, when cribbing had become the only means of breaking the key, makes it seem probable that we derelicted our duty in not studying the early cribs as carefully as we should have done. Once again it was lack of incentive in view of the quick and efficient alphabet method, but had we possessed a crib early in the day, time might have been saved by running a crib where the throw-on menu had proved unsatisfactory. I remember that it was considered a mild sensation when a paired day was broken on a weather-crib very soon after midday - the crib started "ALLE Y PANTELLERIA" and did not appear until right at the end of the N. African campaign.

There is little else to say about Porpoise until the change onto 4 wheels and the abandonment of the throw-on indicating system. Of these changes there will be more said later, but until then breaking proceeded smoothly enough and was little affected by the splitting of the Black Sea area into a separate and similar key on October 1st 1943. Mention should perhaps be made of Porpoise's curious wheel order habits which persisted until March 1943. Instead of the normal 2 days on one wheel


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