Editing History of cryptography (section)

===Japan===
A US Army group, the [[Signals Intelligence Service|SIS]], managed to break the highest security Japanese diplomatic cipher system (an electromechanical [[stepping switch]] machine called [[Purple code|Purple]] by the Americans) in 1940, before the attack on Pearl Harbor. The locally developed Purple machine replaced the earlier "Red" machine used by the Japanese Foreign Ministry, and a related machine, the M-1, used by Naval attachés which was broken by the U.S. Navy's [[Agnes Driscoll]].  All the Japanese machine ciphers were broken, to one degree or another, by the Allies.

The Japanese Navy and Army largely used code book systems, later with a separate numerical additive. [[US Navy]] cryptographers (with cooperation from British and Dutch cryptographers after 1940) broke into several [[Imperial Japanese Navy|Japanese Navy]] crypto systems. The break into one of them, [[JN-25]], famously led to the US victory in the [[Battle of Midway]]; and to the publication of that fact in the [[Chicago Tribune]] shortly after the battle, though the Japanese seem not to have noticed for they kept using the JN-25 system.