Purple CRACKING JAPAN’S ENIGMA

At around 12pm on Saturday 6 December 1941, the Japanese Government in Tokyo instructed its ambassador to the USA, Kichisaburo Nomura, to stand by for a 14-part message. He was ordered to present it to the secretary of state at 1pm the following day, after which he was to destroy the coding machine the message was received on.

Given that it was a weekend, Nomura’s Technical Support staff were away, so he and a fellow diplomat had to decode and transcribe the message themselves. The end result was a message that amounted to a Japanese declaration of war, and was delivered after the planned attack on Pearl Harbor, where more than 2,000 sailors were killed and 18 ships were destroyed. The delays in the delivery of the message meant all those killed were officially non-combatants. The Japanese diplomats seemingly had no prior knowledge of the pending attack.

Astonishingly, the officials also had no knowledge that the message they