6 June 2014
This is the 72nd anniversary of the Battle of Midway, June 4-7, 1942. The American victory is often celebrated as a victory attributable to cryptanalysis: U.S. intelligence had broken the main Japanese naval code. It's important to realize, though, that it wasn't just cryptanalysis. In The Codebreakers, Kahn wrote:
Unknown to Yamamoto, his order was also picked up by the Allied listening posts that ringed the Pacific. Its extreme length indicated its importance, and Fabian's unit … may have first suggested that it might be an operations order.A US Navy history of the battle says
At the same time, Japanese Navy communication activity in the vicinity of Japan dramatically increased…Yes—cryptanalysis was the most important piece of intelligence available. However, the cryptanalysts knew what to work on because of metadata.