Political map of Australia, New Zealand & the Southwest Pacific 23 January 1942 (Japan Comes South): Even as their planes racked Pearl Harbor (Attack on Pearl Harbor), the Japanese were moving south to conquer the resource-rich colonies of Southeast Asia and secure a strategic island perimeter (Greater East Asia Co-Prosperity Sphere). The Americans, British, Dutch and Australians responded by forming a joint command (ABDA) (American-British-Dutch-Australian Command) in an attempt to coordinate a defence.