ABSTRACT
When the Pacific War commenced in December 1941 Australia and its Allies knew little about how to break Japan’s military codes. The US Navy was better prepared to read Japan’s naval codes and when General MacArthur escaped to Australia with his Sigint staff they combined with the Australian decoders who had worked against the Germans in the Middle East to form the Central Bureau. Slowly and persistently these operators broke Japan’s air codes, water transport codes and later the main army code. This analysis explains how this decoding knowledge was slowly accumulated and how it contributed to the ending of the war.
