Rising tension between Japan and the United States stretched back to 1931 with Japan's invasion of Manchuria in the Mukden Incident. Japan's continued aggression, instigating the Second Sino-Japanese War in 1937 and invading French Indochina in 1940—to which the United States and European powers responded with embargoes on iron and oil imports—further heightened the tension. The Japanese thereafter decided to attack the Western powers in Asia, beginning with a surprise attack on the American naval base at Pearl Harbor. When the Japanese struck Pearl Harbor on 7 December 1941, "Mahan" was at sea with the aircraft carrier , three cruisers and four destroyers as part of Task Force 12. "Lexington"s mission was to ferry Marine aircraft to reinforce Midway Island. After news of the attack on Pearl Harbor, the task-force commander received orders to terminate the ferry mission and to search for the Japanese strike force. Unable to locate them, the task force returned to Pearl Harbor on 12 December.