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SCHOOLDAYS 29
as the Turks and the Spanish, proved as interesting and as useful
as those of Germany. Moreover, the traffic of Germany's allies,
such as Japan, could shed a penetrating light on the mindset
of Berlin. Throughout 1941 Hitler held regular meetings with
Baron Oshima, the Japanese Ambassador in Berlin, often
referred to as 'Hitler's Japanese confidant'. Japan had its own
complex cypher, known as 'Magic', produced by a machine
called 'Purple', and Oshima used it to send detailed accounts of
his long conversations with Hitler to Tokyo. 'Magic' had been
broken by the Americans, and early Anglo-American cooperation
on code-breaking ensured that all this was being read in
London. Remarkably, Berkeley Street was also working on the
cyphers of the United States, which did not join the war until
the Japanese attack on Pearl Harbor on 7 December 1941. 42
The dramatic events of 1941 transformed the course of the
Second World War. Although the Battle of Britain had staved
off the possibility of a German invasion, by the summer of 1941
Britain had been fighting for almost two years without a major
victory. Therefore, Hitler's bizarre decision to invade Russia in
June 1941, which required the legions of the Wehrmacht to
turn east, provided a welcome breathing space. After Japan's
attack on Pearl Harbor, Britain, the United States and Russia
found themselves ranged together against the Axis in what was
soon called the 'Grand Alliance'. Welcome as this was, a genuine
world war created new dilemmas for the denizens of Bletchley
Park, who now confronted the ticklish issue of large-scale Allied
cooperation in the business of code-breaking.