The bombing started on Dec. 18, 1972 and lasted 11 days. Waves of B-52s dropped 20,000 tons of ordnance on and near the North Vietnamese capital of Hanoi and the port city of Haiphong.
For the nearly 600 American POWs held by the North Vietnamese, the destruction wreaked by Operation Linebacker II was a signal of their deliverance.
A few weeks after the bombing, on Feb. 12, 1973, the North Vietnamese released the first group of American POWs. The releases continued through March 29.