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40 BLETCHLEY PARK AND BEYOND
sigint organisation was divided between the Army and the Navy,
one of the great problems for the British was cooperating with
one without upsetting the other. Famously, the Americans solved
the tussle over who would decrypt Japanese codes by agreeing
that the Army would decode the material on the even days of
the month, and the Navy on the odd days. A more ludicrous
system for the division of labour would have been hard to devise. 40
GC&CS might have been more centralised than the Americans,
but it had less money. Expanded cooperation with America on
Japan allowed GC&CS to shed some difficult code-breaking tasks.
High-grade Japanese Army cyphers had proved impenetrable for
a decade. By 1941, Bletchley Park was too busy with the European
war, while its Far Eastern code-breakers were struggling to cope
with the mass of material on Japanese espionage derived from
low-level consular intercepts in South-East Asia. On 22 August
1941, Anglo-American cooperation lifted this task from their
shoulders. During talks in Washington, Alastair Denniston
persuaded the US Army that it should 'take over investigation
of Japanese main army cipher soon as priority commitment'.
Shortly after, Captain Geoffrey Stevens from Singapore travelled
to Washington carrying all the British material on the Japanese
main army cypher.41 The British were glad to see the back of it.
At the end of the war approximately 2,500 Americans would still
be working on this one Japanese cypher to no avail.
All the while, Britain was also de cyphering some American
traffic. Amongst the decrypts selected for the personal perusal of
Winston Churchill were those of many Allied and neutral countries.
GC&CS was clearly working successfully on the American
diplomatic code 'Grey' until December 1941.42 Remarkably, there
was no embarrassment about this. In June 1941, while discussing
comprehensive sharing of Far East intelligence, the British asked
the US Military Attachc\ General Raymond Lee, for his opinion
on the security of American cyphers. This was the conduit through
which sigint would pass between London and Washington. Lee
replied tardy that the GC&CS already knew a great deal about
this matter. He recorded in his diary: