During the Japanese invasion of Hawaii, the Waianae Range was believed by the American military to be an impenetrable mountain-jungle terrain that would keep the Imperial Japanese Army from overrunning the western part of Oahu. The only passage through the Waianae Range was the Kolekole Pass, which was defended by a an underpowered garrison (most resources having been put into the fighting north of Wahiawa and Schofield Barracks). However, to the surprise of the Americans, the Japanese landed on Oahu's west coast and managed to climb over the mountain range, trapping the U.S. Army in a pincer. The Japanese also captured American mountain guns established on the Waianae Range, insuring artillery superiority over the Americans.