The surprise attack by Japanese aircraft and midget submarines on the U.S. Navy’s anchorage at Oahu, Hawaii, on Sunday, 7 December 1941 led to the United States’ entry into World War II. The intelligence failure that allowed the Japanese carrier battle fleet to steam towards the Hawaiian Islands without being detected was the subject of several congressional investigations, the first of which apportioned blame to Admiral Kimmel for concentrating the Pacific Fleet where it made an easy target for enemy torpedoes and bombers.
The disaster was all the more inexcusable because American cryptographers had gained access to some of the Japanese diplomatic and naval ciphers, and as Tokyo’s wireless traffic was read, it became evident that the increasingly tense telegrams contained obvious clues to an imminent breakdown in diplomatic relations and an air raid on Pearl Harbor and American bases in the Philippines.