March 18, 1970: Prince Norodom Sihanouk deposed in Cambodia

By Florian Sohnke

To most critics of America’s Vietnam policy, the existence of a centralized operations center coordinating communist insurgency in South Vietnam only existed in the minds of President Nixon, National Security Adviser Henry Kissinger and the cast of high-ranking officers at the top of the defense pyramid in the Pentagon.

Hamstrung by Democrats in Congress and the anti-war movement, military assistance to Cambodia was limited and largely rested on captured weapons from Viet-Cong guerillas in South Vietnam sent to the Sihanouk government in Phnom Penh.

Frustrated by the Johnson Administration’s refusal to expand the war in South Vietnam, Military Assistance Command Vietnam (MACV) commander, General Creighton Abrams, welcomed the election of President Richard M. Nixon. In Nixon, Abrams knew he had a man committed to fighting a more aggressive war against communist insurgents, the Viet-Cong (VC) and North Vietnamese (NVA) regulars, who often sought refuge in neighboring Cambodia.

tinntarOne obstacle remained to waging a larger war: Prince Norodom Sihanouk, leader of Cambodia

Desperate to keep his country out of the war, Sihanouk maintained a neutral stance and tolerated the persistent infringement of Cambodian neutrality and sovereignty by VC and NVA troops huddled inside his country. From these sanctuaries, communist guerrillas and NVA troops regularly conducted raids inside South Vietnam.

To President Nixon, Henry Kissinger and General Abrams, this was an unacceptable political and military situation.

Suffering from minor health problems, Prince Sihanouk departed for a trip to Europe and to seek treatment in France in February. Temporarily replaced by Prime Minister Lon Nol and his deputy, Sirik Matak, the two would conspire with an exiled Sihanouk foe, Son Ngoc Thanh, to overthrow Sihanouk with the support of local American military and intelligence officials.

Despite endless speculation the conspirators were inspired by the Central Intelligence Agency (CIA), no evidence has ever been unearthed to connect the American intelligence organ to the planned coup. Dark hints of local encouragement from U.S. embassy officials and military personnel have merit, but according to Henry Kissinger, the events of March 18, 1970 took the White House completely by surprise.

Although Nol claimed he had been coerced at gunpoint by Matak to sign documents calling for Sihanouk’s ouster, on March 18, 1970, Cambodian army units loyal to Nol and Matak surrounded the capital and the Cambodian National Assembly. Nol took the podium, cited Article 122 of the Cambodian constitution, which provided for a “no-confidence” vote in Sihanouk and immediately formed the Khmer Republic.

Nol’s first official act was to demand North Vietnamese and Viet-Cong personnel leave Cambodia. Forthwith, he reached out to the United States and requested economic and military aid and approved an intensification of American bombing missions over Cambodia.

Six weeks later, a joint-U.S.-Army of the Republic of South Vietnam (ARVN) military operation was launched into Cambodia with the mission of locating Central Office for South Vietnam (COSVN) and destroying communist military positions in Cambodia.

Lasting approximately two months, U.S. and ARVN forces never found one major operations center directing communist shenanigans in South Vietnam; however, troops did uncover hundreds of concealed bunkers containing several hundred tons of weapons and ammunition.

The haul, likely hoarded for a planned offensive into South Vietnam in late 1970 or early 1971, was destroyed.

Norodom Sihanouk
Norodom Sihanouk

Outraged by his overthrow, Sihanouk joined the communists and remained a figurehead for a Cambodian government in exile in Beijing until his return in 1975. Expelled by the communists, he sought refuge in Beijing and returned to reign in Cambodia until he stepped down in 1994.

He died in Beijing in 2012.