Systematic U.S. aerial operations against the Ho Chi Minh Trail had begun on 14 December 1964 with Operation Barrel Roll. With the onset of Operation Rolling Thunder, the strategic aerial bombardment of North Vietnam in April 1965, the U.S. also expanded its interdiction effort in Laos by dividing the Barrel Roll area into two sections on 3 April. The former operation would continue in northeastern Laos while Operation Steel Tiger was initiated in the southern panhandle. The American headquarters in Saigon requested, and received, authorization to control bombing in the area adjacent to South Vietnam's northern provinces in Operation Tiger Hound on 3 December 1965. The U.S. Air Force had already begun to up the ante in its anti-infiltration campaigns by unleashing B-52 Stratofortress bombe