In a post Second World War order in which nations belonged to either the camp led by the United States or by the Soviet Union, Cambodia was a nonaligned country. At the 1954 Geneva Conference, it had been agreed that all foreign forces would withdraw from Cambodia, that it would refrain from joining any military alliance, and that no foreign bases would be established on its sovereign territory.
In relations with more powerful forces affecting his nation and with competing factions in his own country, Cambodian Head of State Prince Norodom Sihanouk was a master of the balancing act and a survivor. Alarmed by growing anarchy in South Vietnam, Cambodia severed diplomatic ties with Saigon in August 1963. A 1965 deal with China and North Vietnam allowed Viet Cong and North Vietnamese forces to build permanent military facilities on Cambodian territory, while opening Cambodian ports to shipments of military supplies from China and the Soviet Union destined for their Vietnamese communist allies.
In the late 1960s, Sihanouk moved to improve relations with the West. Eastern Cambodia had been serving as the southern terminus of the Ho Chi Minh Trail and as a sanctuary for North Vietnamese military units, putting Cambodian neutrality in jeopardy. The Cultural Revolution made China a difficult partner to deal with, politically and economically. South Vietnam had not collapsed, even in the face of the 1968 Tet Offensive. A loss of economic and military aid from the United States and the unavailability of American military equipment and spare parts caused Phnom Penh to have second thoughts about its break with Washington. Concurrently, newly inaugurated U.S. President Richard Nixon, seeking to withdraw from Southeast Asia under honorable conditions, perceived a means of helping his policy of Vietnamization to succeed.
The Central Office for South Vietnam
The Central Office for South Vietnam (COSVN) was organized in 1961 by the Central Committee of the Workers Party of Vietnam (the Communist Party) in Hanoi, to direct Viet Cong political and military operations in South Vietnam. People's Army of Vietnam General Nguyễn Chí Thanh, a member of the Workers Party of Vietnam political bureau, arrived in late 1963 or early 1964 to serve as COSVN's leading strategist and military commander. He continued in that role through late 1967, when he returned to Hanoi to deliver his plan for the Tet Offensive and died of a heart attack while there.
On the ground, the organization was composed of individuals living in thatched huts in jungle surroundings, constantly on the move in order to avoid U.S. bombing raids and search and destroy operations. American or South Vietnamese Special Forces teams inserted into COSVN territory usually wound up dead or returning with heavy casualties.
During the early 1960s, COSVN was located northwest of Saigon, near South Vietnam's border with Cambodia. Later in the 1960s, the headquarters was in and around Cambodia's "Fishhook" region, a salient protruding into Vietnamese territory approximately 80 kilometers northwest of Saigon. In February 1967, the United States attempted to wipe out COSVN in Operation Junction City, an 82-day airborne operation northwest of Saigon, near the Cambodian border. The Viet Cong, with intelligence sources embedded deep within the South Vietnamese government, preempted this grand operation by relocating COSVN headquarters to Cambodia.
On February 22, North Vietnam launched its Tet 1969 offensive, a coordinated series of sapper attacks and artillery or rocket bombardments against military targets, primarily around Saigon and Da Nang. These attacks were quickly repulsed, albeit at a steep cost: More than 1,140 Americans and 1,500 South Vietnamese were killed over three weeks of fighting.
Nixon determined to follow through on suggestions recently made by top defense officials: Chairman of the Joint Chiefs Earle Wheeler had urged Nixon to bomb North Vietnamese sanctuaries in eastern Cambodia, and commander of the Military Assistance Command in Vietnam Creighton Abrams had proposed bombing COSVN. U.S air power would provide a shield for the withdrawal from Vietnam and the process of Vietnamization.
The result was Operation Menu, a covert series of six B-52 "carpet bombing" missions against targets in eastern Cambodia that started on March 18, 1969 and ended on May 26, 1970. The first mission consisted of a humongous raid by 60 B-52 Stratofortress strategic bombers flying out of Andersen Air Force Base in Guam, targeting COSVN in the Fishhook region. COSVN was not destroyed in the raid.
The Studies and Observations Group
The MACV Studies and Observations Group was a highly classified, special operations unit which conducted covert unconventional warfare operations during the Vietnam War. The SOG reported directly to the Special Assistant for Counterinsurgency and Special Activities at the Pentagon, but formally belonged to the Military Assistance Command, Vietnam; hence the acronym MACV-SOG. They conducted strategic reconnaissance missions in South Vietnam, North Vietnam, Laos, and Cambodia, capturing enemy prisoners and rescuing downed pilots and prisoners of war. They carried out clandestine agent team activities and psychological operations against the North Vietnamese government. The Studies and Observations Group was a multi-service organization, although direct action and reconnaissance missions were conducted almost exclusively by U.S. Army Green Berets.
Beginning in 1967, MACV-SOG reconnaissance teams were sent to obtain military intelligence on North Vietnamese base areas in Cambodian territory. This information would be presented to Prince Sihanouk, to convince him to uphold Cambodia's officially neutral status. During Operation Menu, MACV-SOG forward air controllers provided the majority of bomb damage intelligence.
In Secret Commandos: Behind Enemy Lines with the Elite Warriors of SOG, author John Plaster describes a bombing assessment mission conducted after an Operation Menu attempt to obliterate COSVN. A seventy-man "Hatchet Force" was dropped by helicopter into a scene of incredible devastation. As the choppers pulled away, the landing zone turned into an instant killing zone, as if the enemy had been sitting and waiting for them to land in that exact spot. The same thing had happened in the bombing assessment performed following the previous Operation Menu air raid. Commanders were forced to reconsider security inside SOG, as there had already been suspicions of an enemy mole in their Saigon headquarters.