query: When did construction on Caribou Air Force Station begin?
passage: Loring Air Force Base
In 1951, the Department of Defense (DOD) allocated funds for the construction of an ordnance storage site at Loring AFB. The designs called for a self-sufficient "maximum security storage area for the most advanced weapons of mankind". The mission of the facility would be the protection and maintenance of the weapons used by SAC. The facility was in the northeast corner of the base, and construction began on 4 August 1951. In addition to 28 storage igloos and other weapons storage structures, the facility included weapons maintenance buildings, barracks, recreational facilities, a warehouse, and offices.[19]
passage: Caswell Air Force Station
Caswell was one of twenty-eight stations built as part of the second segment of the permanent Air Defense Command network. Prompted by the start of the Korean War, on July 11, 1950, the Secretary of the Air Force asked the Secretary of Defense for approval to expedite construction of the second segment of the permanent network. Receiving the Defense Secretary’s approval on July 21, the Air Force directed the Corps of Engineers to proceed with construction.