During World War II, the Japanese seized the Aleutian Islands of Attu and Kiska, located off the tip of Alaska, in June 1942. These islands provided the Japanese with a base from which to limit Allied air and sea operations in the North Pacific. They attacked Dutch Harbor on the island of Unalaska on June 3rd and 4th, 1942, seeking to destroy U.S. Army and Navy operations near the city of Unalaska. In an effort to recapture Attu and Kiska, the United States established airfields on Adak and Amchitka Islands in Aug. 1942. Plans were made in the spring of 1943 to recapture Attu, and American and Canadian air and naval forces landed there on May 11, 1943. The Japanese defended their position intensely, and the fighting continued until May 30, when Japan announced the loss of the island.

On August 15, 1943, a powerful Allied amphibious force, including a U.S. infantry division and elements of the Royal Canadian Army, assaulted the island of Kiska, where the Japanese had developed their largest base. To the surprise of the Allies, they found that the Japanese, under cover of heavy summer fog, had secretly evacuated the island. Kiska was declared secure, thus ending the Aleutian Islands Campaign. During 1944, the Canadians left and U.S. Army presence in Alaska dropped from 144,000 to 63,000 personnel. Although interest in the Alaskan theater waned, it marked the Allies' first theater-wide victory in World War II and ended Japan's only campaign in the Western Hemisphere.