Pearl Harbor Intelligence Failure

The 1941 surprise attack that exposed fatal gaps in American intelligence coordination

Overview

The Japanese strike of December 7, 1941 caught American intelligence dispersed and stovepiped. Cryptanalysts were reading diplomatic traffic through MAGIC but not naval codes, fragments pointed to a break in relations rather than to a target, and no mechanism fused signals across services. Ten official inquiries followed, documenting missteps without proving specific foreknowledge of Hawaii. The failure shaped the National Security Act of 1947, which created the CIA and unified command precisely to prevent its repetition. The army and navy each held pieces of the Japanese picture but no shared watch list.