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Original Radar Plot of Detector Station Opana, Oahu, Hawaii, December 7, 1941

At 7:20 a.m. on December 7, 1941, two novice radar operators detected aircraft approaching Oahu. Their control officer believed the signals tracked American B-17s, but by 7:55 a.m., the first wave of Japanese bombers attacked Pearl Harbor. A 1945 Congressional investigation of the surprise attack examined this radar plot.

Records of the Joint Committees on Congress, National Archives and Records Administration

Original Radar Plot of Detector Station Opana

Declaring War Against Japan

America’s geographic isolation from the conquests of the Empire of Japan in Asia and the Nazi alliance in Europe ended with Japan’s attack on Pearl Harbor. Within days, Congress passed declarations of war against Japan, Germany and Italy. Both the armed forces and the civilian home front were organized to win the war. Congress appropriated the necessary funds to support the war effort and worked closely with the executive branch.