The attack on Clark Field was part of a series of morning airstrikes on United States Pacific island military bases opening Japanese participation in World War II. The attack was intended to minimize interference from the Far East Air Force (FEAF) during the subsequent invasion of the Philippines by the Empire of Japan. Capture of the Philippines was essential to control shipping routes between Japan and the Greater East Asia Co-Prosperity Sphere. Hostilities were initiated by the attack on Pearl Harbor at 07:48 Hawaiian Time (UTC-10) on 7 December 1941. As dawn moved westward across the Pacific (and the International Date Line), daylight airstrikes followed at mid-day (UTC+12) on Wake Island, at 09:27 (UTC+10) on Guam, at 06:00 (UTC+8) on Davao, at 09:30 (UTC+8) on Baguio and at 12:35 (UT