During World War II, the United States Army Air Forces engaged in combat against the air, ground and naval forces of the Empire of Japan in the South West Pacific Theatre. As defined by the United States Department of War, the South West Pacific theatre included the Philippines, the Dutch East Indies (excluding Sumatra), Borneo, Australia, the Australian Territory of New Guinea (including the Bismarck Archipelago), the western part of the Solomon Islands and some neighbouring territories. The theatre took its name from the major Allied command, which was known simply as the "South West Pacific Area".