On 18 March 1970, Cambodia's chief of state, Prince Norodom Sihanouk, was overthrown by the National Assembly led by the pro-American Defense Minister, General Lon Nol).

[2] These border sanctuaries and Base Areas were of strategic significance to the North Vietnamese effort in South Vietnam, however, and they were not going to give them up without a fight.

For the past year and half, Abrams had also been bombarded by requests for the authorization of airstrikes by the highly-secret Military Assistance Command, Vietnam Studies and Observations Group or SOG.

[3] On 18 April, Abrams requested authority from the Joint Chiefs of Staff to utilize U.S. tactical aircraft based in South Vietnam for a 30-day period.

These aircraft would be acting in concert with Operation Menu, the highly classified bombing of PAVN sanctuaries and Base Areas in eastern Cambodia by USAF B-52 bombers.