It was the sea war that would become Alan's particular province.
In early 1940 the different Enigma systems were divided among the chief crypt-analysts, who were allocated huts outside the Bletchley mansion.
Welchman took over the army and air force Enigma systems, in Hut 6, joined by a number of new recruits.
Dillwyn Knox took the Italian Enigma and that used by the German SD, again with new recruits.
These systems, which did not use plugboards, suited his psychological methods.
And Alan was allocated Hut 8 in which to head the work on the naval Enigma signals.
Other huts housed sections translating and interpreting the output;
thus Hut 3 dealt with the army and air force material issuing from Hut 6, while the naval signals, if and when any were produced, would be interpreted by Hut 4, which was headed by Frank Birch.
Alan probably knew little of the context in which he was working, apart from the general air of urgency that issued from Hut 4.
This was probably just as well, for the context was not exactly an encouraging one.
He was working for the Admiralty, which only grudgingly had relinquished naval cryptanalysis to GC and CS.