Abstract On December 7, 1941, military forces of the Empire of Japan successfully attacked United States army and naval installations on the island of Oahu, Hawaii. The success of the surprise attack was due, in part, to the failure of American commanders in Washington, D. C. The Army Chief of Staff and the Chief of Naval Operations failed to ensure that needed intelligence and diplomatic information reached their field commanders in Hawaii. Analysis of the military command structure, communication system, and the personalities of the chief commanders, General George C. Marshall and Admiral Harold R. Stark, will provide a new insight into America’s greatest military disaster. This paper is a military assessment; political and economic aspects are used only in relation to the military perspective. Primary sources are diaries, newspapers, correspondence, government documents, and books written by the participants in the events. Secondary sources provide the necessary background material relevant to the period.