Pearl Harbor: 12 Facts and Myths About the Japanese Attack on the U.S. Pacific Fleet

2. Myth: The U.S. Had No Warning

While the attack on Pearl Harbor was a surprise, there were intelligence signals that U.S. forces missed. Declassified documents reveal that the FBI shared information about Japanese interest in U.S. defenses in Hawaii, including a double agent’s report indicating Japanese efforts to obtain details about Pearl Harbor’s defenses (cia.gov). Additionally, the Army’s Signal Intelligence Service intercepted a Japanese diplomatic message on December 6, 1941, indicating that war was imminent.