The Dutch Harbor Naval Operating Base and Fort Mears are the two military installations built next to each other in Dutch Harbor, on Amaknak Island of the Aleutian Islands in Alaska, by the United States in response to the growing war threat with Imperial Japan. In 1938 the Navy Board recommended the construction which began in July 1940. The first army troops arrived in June 1941 and the navy air base was finished in September 1941. At the time of the attack on Pearl Harbor, these were the only military installations in the Aleutian Islands.DescriptionDutch Harbor occupies the central portion of Amaknak Island, a small island in Unalaska Bay which is separated from the larger Unalaska Island by Iliuliuk Bay. The two islands are joined joined by a bridge connecting the city of Unalaska to the southern portion of Amaknak Island. During World War II the entirety of Amaknak Island was used by the United States Navy as an operating base, and by the United States Army, which manned coastal defenses on the high ground at the northern and southern parts of the island. The central portion of the island was occupied by the facilities of the naval base, which included a runway and other aircraft support facilities, munitions storage facilities, barracks, a hospital, and a bomb-proof power plant. South of the naval base was Fort Mears, (named in tribute to Frederick Mears) which primarily consisted of barracks for the troops manning the coastal defenses. The coastal defenses included batteries placed to the north on Ulakta Head and Mount Ballyhoo, and to the south on what the army called Hill 400, but is now known as Bunker Hill for its surviving structures.