Primary Sources: Vietnam War

Operation Linebacker was the codename of a U.S. Seventh Air Force and U.S. Navy Task Force 77 air interdiction campaign conducted against North Vietnam from 9 May to 23 October 1972, during the Vietnam War. Its purpose was to halt or slow the transportation of supplies and materials for the Nguyen Hue Offensive (known in the West as the Easter Offensive), an invasion of South Vietnam by forces of the People's Army of Vietnam (PAVN) that had been launched on 30 March. The linebacker was the first continuous bombing effort conducted against North Vietnam since the end of Operation Rolling Thunder in November 1968. Wikipedia

Operation Linebacker II was an aerial bombing campaign conducted by the U.S. Seventh Air Force and U.S. Navy Task Force 77 against targets in the Democratic Republic of Vietnam (North Vietnam) during the final period of U.S. involvement in the Vietnam War. The operation was conducted from 18 to 29 December 1972, leading to several informal names such as "The December Raids" and "The Christmas Bombings". In Vietnam, it is just simply called "12 days and nights" (12 ngày đêm) and "Operation Dien Bien Phu in the air" (Chiến dịch Điện Biên Phủ trên không) or just simply "Dien Bien Phu in the air" (Điện Biên Phủ trên không). Unlike the Operation Rolling Thunder and Operation Linebacker air interdiction operations, Linebacker II was designed to be a "maximum effort" bombing campaign to "destroy major target complexes in the Hanoi and Haiphong areas, which could only be accomplished by B-52s". It saw the largest heavy bomber strikes launched by the U.S. Air Force since World War II. Wikipedia