The Japanese invaded the Philippines shortly after Pearl Harbor, bringing the Harbor Defenses of Manila and Subic Bays into the war along with the other U.S. and Filipino forces in the archipelago. The Japanese initially landed in northern Luzon, far from the defenses of Manila Bay. Although the Coast Artillery did their best, their weapons were poorly positioned against the direction of enemy attacks and vulnerable to air and high-angle artillery attack. Eight 8-inch railway guns had been deployed to the Philippines in 1940, but six were destroyed by air attack while entrained in response to the initial landings, and the other two were placed in fixed mountings on Corregidor and Bataan, but lacked crews and ammunition. The 14-inch turret guns of Fort Drum and the 12-inch mortars of Battery Way and Battery Geary were probably the most effective coast defense weapons in the Battle of Corregidor, but all but two of the mortars were knocked out before the Japanese landed on the island. The U.S. forces surrendered on 6 May 1942, after destroying their weapons.