Primary Sources: Vietnam War

Operation Menu was a covert United States Strategic Air Command (SAC) tactical bombing campaign conducted in eastern Cambodia from 18 March 1969 to 26 May 1970 as part of both the Vietnam War and the Cambodian Civil War. The targets of these attacks were sanctuaries and base areas of the People's Army of Vietnam (PAVN — commonly referred to during the Vietnam War as the North Vietnamese Army [NVA]) and forces of the Viet Cong (VC), which used them for resupply, training, and resting between campaigns across the border in the Republic of Vietnam (South Vietnam). The impact of the bombing campaign on the Khmer Rouge guerrillas, the PAVN, and Cambodian civilians in the bombed areas are disputed by historians.

An official the United States Air Force record of US bombing activity over Indochina from 1964 to 1973 was declassified by US President Bill Clinton in 2000. The report gives details of the extent of the bombing of Cambodia, as well as of Laos and Vietnam. According to the data, the air force began bombing the rural regions of Cambodia along its South Vietnam border in 1965 under the Johnson administration; this was four years earlier than previously believed. The Menu bombings were an escalation of what had previously been tactical air attacks. Newly inaugurated President Richard Nixon authorized for the first time the use of long-range Boeing B-52 Stratofortress heavy bombers to carpet bomb Cambodia.

Operation Freedom Deal immediately followed Operation Menu. Under Freedom Deal, the B-52 bombing was expanded to a much larger area of Cambodia and continued until August 1973. Wikipedia