The military history of the Aleutian Islands began almost immediately following the purchase of Alaska from the Russian Empire by the United States in 1867. Prior to the early 20th century, the Aleutian Islands were essentially ignored by the United States Armed Forces, although the islands played a small role in the Bering Sea Arbitration when a number of British and American vessels were stationed at Unalaska to enforce the arbitrators' decision. By the early 20th century, a number of war strategies examined the possibility of conflict breaking out between the Empire of Japan and the United States. While the Aleutian Islands were seen as a potential staging point for invasions by either side, this possibility was dismissed owing to the islands' dismal climate. In 1922, the Washington Naval Treaty was signed, after which the United States Navy began to take an interest in the islands. However, nothing of significance was to materialize until World War II.
In June 1942, the Imperial Japanese Navy invaded and captured Attu Island and Kiska. This marked the first time in 130 years that United States soil was under occupation by a hostile country and was the only two invasions of the United States during World War II. The Americans wanted to recapture the two islands, and in January the following year began their advance by capturing Amchitka without opposition. On March 26, the Battle of the Komandorski Islands ensued after the United States Navy imposed a naval blockade on the two islands to reduce the opportunities for the Japanese to keep their Attu and Kiska bases supplied. In May, Attu Island was recaptured, with a total of almost 3,000 deaths from both sides combined. The Americans then prepared to attack Kiska in August, only to find that the entire island had been evacuated by the Japanese in late July. During the recapture of Kiska by the United States, 92 men died as a result of friendly fire and a mine, despite no Japanese soldiers being present on the island.
During the 1960s and early 1970s, the United States Atomic Energy Commission (AEC) executed a number of nuclear tests on the island of Amchitka in the face of vehement opposition from environmental and local indigenous groups. The first test, conducted in 1965, caused significant damage to the surrounding area, although the details of this damage were not released to the public until 1969. In 1969, the AEC executed a 'calibration shot' to determine whether Amchitka would be suitable for future tests. In 1970, the AEC announced plans to detonate a bomb named 'Cannikin', set to release a blast 385 times that released by the dropping of an atomic bomb on Hiroshima in 1945. After a United States Supreme Court challenge to the testing failed by one vote, the testing proceeded as scheduled in November 1971.