Cracking the enemy's radio code is a task so urgent and so difficult that it demands the military's best minds and most sophisticated technology. But when the coded messages are in a language as complex as Japanese, decoding problems multiply dramatically. It took the U.S. Army a full two years after the attack on Pearl Harbor to break the codes of the Japanese Imperial Army. But by 1944 the U.S. was decoding more than 20,000 messages a month filled...