The Japanese invaded northern Luzon a few days after the attack on Pearl Harbor on 7 December 1941 that brought the US into the war. They advanced rapidly, with other landings elsewhere, notably at Legazpi in southeast Luzon on 12 December, Davao on Mindanao on 20 December, and Lingayen Gulf on 22 December. On 26 December 1941 Manila was declared an open city, with the Philippine government and MacArthur's headquarters evacuated to the Malinta Tunnel. Amid the evacuations, a re-inauguration ceremony for Philippine President Manuel Quezon's second term was held just outside the tunnel on 30 December. The Japanese entered Manila on 2 January 1942. Five days later the U.S. and Philippine forces completed a fighting withdrawal to the Bataan peninsula, northwest of Corregidor, and prepared to defend it. In the northern Philippines, this left only Bataan, Corregidor, and Forts Hughes, Frank, and Drum in Allied hands. This situation had been anticipated in the prewar War Plan Orange-3, under which the forces in the Philippines were expected to hold out at the mouth of Manila Bay for six months. By that time it was anticipated that a relief expedition from the U.S. might arrive. General MacArthur had hoped to defend the Philippines more aggressively under the Rainbow Plan, and was able to get some reinforcements in the months prior to the U.S. entering the war, but this fell apart with the rapid Japanese advance in December 1941. And, with almost all of the Pacific Fleet's battleships sunk or damaged at Pearl Harbor, and the Japanese advancing in several parts of Southeast Asia at a much greater rate than expected, no relief was organized. Although extensive guerrilla operations were conducted by Filipinos with U.S. support, U.S. forces did not return to the Philippines in strength until the invasion of Leyte Gulf in October 1944.