The US Army and Navy shared responsibility for the defense of Pearl Harbor in 1941
In January 1941, Secretary of the Navy Frank Knox wrote to Secretary of War Henry L. Stimson, “If war eventuates with Japan, it is believed easily possible that hostilities would be initiated by a surprise attack upon the fleet or the naval base at Pearl Harbor”. Knox went on to identify defenses against air attack, which he deemed “probable”, as inadequate. Knox urged coordination and cooperation between the Navy and Army to defend the installations, though the defense of the island was entirely the responsibility of the Army. Stimson forwarded the letter, with an endorsement supporting its recommendations, to Admiral Husband Kimmel, Commander in Chief Pacific Fleet, and General Walter Short, Commander of the Army’s Hawaiian Department. Through his actions, it was evident Short did not concur with Knox’s assessment of the situation in Hawaii.
Short believed the greatest danger faced by the US Army Air Forces on the Hawaiian Islands came from potential saboteurs, rather than the Japanese Navy. In order to protect his airplanes from sabotage, he ordered them parked in rows on the airfields, wingtip to wingtip, rather than dispersed to protect them from aerial attacks. Short received several war warnings in the week leading up to December 7. In his post-attack defense, he claimed the warnings were vague and did not specifically tell him what to do. He also blamed Navy reconnaissance for not providing him with adequate warnings of Japanese activities. When the Japanese attacked, most of the airplanes the Americans lost that day were destroyed on the ground, the neat rows providing easy targets for the attacking Japanese. The Army relieved Short of his command on December 17, 1941.