The Aleutian Islands campaign was a military campaign conducted by the United States, Canada, and Japan in the Aleutian Islands, part of the Territory of Alaska, in the American Theater and the Pacific Theater of World War II starting on June 3, 1942. In the only two invasions of the United States during the war of a U.S. incorporated territory, a small Japanese force occupied the islands of Attu and Kiska, where the remoteness of the islands and the challenges of weather and terrain delayed a larger American-Canadian force sent to eject them for nearly a year. Successful Japanese invasions of other U.S. territories, which were unincorporated territories, in the western Pacific shortly after the Attack on Pearl Harbor included Wake Island, Guam, and the Philippines. The islands' strategic