Marching Orders: The Untold Story of How the American Breaking of the Japanese Secret Codes Led to the Defeat of Nazi Germany and Japan

by Bruce Lee

According to Currier, in 1946, after the congressional hearings into Pearl Harbor, the Navy assigned a group of cryptologists to study some twenty thousand previously unread JN-25 intercepts. Of this number, one thousand intercepts made prior to Pearl Harbor were carefully analyzed. “In these particular intercepts,” says Currier, “there are a couple of dozen messages that give enough solid evidence to show the Japanese are going to attack Pearl Harbor.”7 It is not until 1946, then—five years after Pearl Harbor—that the U.S. Navy knows for sure that the JN-25 codes carried specific information that could have prevented Pearl Harbor.