Conspiracy theorists have long contended U.S. leaders withheld from Pearl Harbor commanders a key warning that war with Japan was imminent. In fact, however, the preattack message was a figment of the chief Navy code-breaker's imagination.
The 7 December 1941 attack on Pearl Harbor by Imperial Japanese Navy planes achieved complete surprise. So unexpected was such an attack, in fact, that even the discovery of Japanese midget submarines at the mouth of Pearl Harbor or the tracking of unknown aircraft approaching Oahu by U.S. Army radar never raised a general alarm among American forces. Considering the skillful planning and execution of the Japanese operation and its subsidiary radio-deception scheme, the degree of surprise was understandable.