Cryptographic History of Work on the German Naval Enigma

technique was much less developed and there were other handicaps [stemming?] from lack of knowledge of the traffic. It was a notable occasion.

30. May 7th, the paired day, was speedily broken and a fortnight later April 14th was broken - a positive blitzkrieg in those days. This second success depended on the first since the May 7/8th break resulted in a great improvement in the table used on April 14th. Later still June 27th was broken - it having been established that the bigram tables had not been changed on June 1st after all, but on July 1st - and finally, in February 1941, April 28th was broken on a crib, the first success the bombe had had on a crib run through all 336 W.O's. This was almost immediately followed by the LOFOTEN pinch, in which as a result of a raid - planned with this end in view - on the Norwegian coast the keys for the complete month of February 1941 were captured.


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