The following editorial has been adapted from William J. Rust‘s presentation, Plausible Denial: Eisenhower and the Dap Chhuon Coup, during a panel on Cambodia and the United States during the Cold War at the 2016 SHAFR (Society for Historians of American Foreign Relations) Annual Meeting.
Covert Action in Cambodia
My most recent book, Eisenhower and Cambodia, discusses the failed attempt to overthrow neutralist prime minister Prince Norodom Sihanouk in 1959. More specifically, it presents new information and analysis about the origins of US involvement in plotting against Sihanouk and about the role of the US government in the botched attempt to topple him.
The unsuccessful coup is significant for at least two reasons: One, US relations with Sihanouk were severely—if not fatally—damaged not only by the exposure of CIA involvement in the plot, but also by the failure of the US government to provide any explanation for agency operative Victor M. Matsui’s contacts with the rebels. Two, the unsuccessful coup was part of a larger pattern of counterproductive efforts by the Eisenhower administration to overthrow two other Southeast Asian neutralists: Prime Minister Souvanna Phouma of Laos and President Sukarno of Indonesia.
Although a large majority of Cambodians favored Sihanouk’s policy of neutrality, an anticommunist minority was disturbed by the prince’s visit to the People’s Republic of China in February 1956. One member of that minority was Colonel Chhuon Mochulpich, better known as Dap Chhuon. A former dissident who rallied to the government in 1949, he was a regional commander who had thus far ruthlessly suppressed all opposition to Sihanouk. In March 1956, however, Dap Chhuon wrote a confidential letter to Robert M. McClintock, the US ambassador in Phnom Penh, informing the diplomat that he was “awaiting a favorable opportunity to frustrate” Sihanouk’s neutrality policy. The letter to McClintock was the impetus for US deliberations about the possibility of “Sihanouk’s removal.”
As a matter of policy, the Eisenhower administration covertly supported Sihanouk’s anticommunist opposition. Dap Chhuon, with assistance from the South Vietnamese and Thai governments, moved against Sihanouk in February 1959, demanding the installation of a pro-western government and threatening Sihanouk with guerrilla warfare. Apparently hoping that his fierce reputation would encourage negotiations, if not capitulation, Dap Chhuon was surprised when a convoy of armored cars and trucks arrived at his headquarters in Siem Reap to arrest him for treason. His rebellion collapsed without a shot being fired. He fled into the jungle and was killed by Sihanouk’s security forces.
The Cambodian armed forces captured two Vietnamese in Dap Chhuon’s villa, as well as gold bars, documents, and communications equipment. The royal army also seized his brother, Slat Peau. At his treason trial later in the year, Slat Peau testified that he had received the gold bars from a South Vietnamese agent and a radio from Victor Matsui, a Japanese-American who worked for the CIA. The radio, Slat Peau said, allowed Dap Chhuon to communicate with the “American Embassy [in] Phnom Penh” and with the other conspirators. Slat Peau’s testimony, likely coerced and arguably unreliable, nonetheless raises questions about the precise role of the US government in the plot.
Some US officials have claimed that the CIA merely reported on Dap Chhuon’s activities and that the US government tried to stop his coup. Other officials have stated that the United States played an active role in supporting the conspiracy. The conflicting claims about the degree of US involvement in the coup could be resolved by more enlightened declassification of fifty-five-year-old government documents. There is, however, a theory that accommodates the differing accounts: Sometime in early 1959, senior officials in Washington agreed to provide deniable covert assistance—gold bars, radio equipment, and other support—to South Vietnam and Dap Chhuon. Although there is no “smoking gun” document currently available that proves this conclusion, there is evidence that US officials believed Dap Chhuon’s plot could succeed. Moreover, there is a declassified document with the text of a State Department cable to Elbridge Durbrow, the US ambassador to South Vietnam.
Dated February 2, 1959, the cable was transmitted to Saigon via CIA channels, a more secure means for State Department discussions of covert activities. Aware of the disastrous implications of a failed coup, department officials instructed Durbrow to “be prepared [to] approach President [Ngo Dinh] Diem on short notice” if, in the ambassador’s “opinion,” South Vietnam’s “activities [were] endangering [the] situation [in] Cambodia.” Durbrow should then emphasize to Diem, “[The] US cannot see [the] chance for [a] successful coup [in] Cambodia under present conditions.” In other words, in early February Durbrow was given discretionary authority to intervene with Diem and attempt to pull the plug on the coup if it appeared unpromising. Durbrow did not, however, exercise this authority until after “Diem was irremediably committed” to the conspiracy, according to William Trimble, the US ambassador to Cambodia and the official most responsible for damage control after the debacle.
Sihanouk emerged from the failed coup with enhanced prestige, forcing the Eisenhower administration to conclude that covert intervention in Cambodia’s internal affairs had been “an obstacle to the pursuit of our objectives.” Many years later, Trimble summarized this conclusion more bluntly: “The Dap Chhuon operation was stupid, very stupid.” In 1960, the National Security Council policy directive for Cambodia was formally amended “to eliminate language which might provide a basis for further abortive coup plots.” Although acknowledging the prince’s popularity and political power, the new policy did not mean that senior Eisenhower administration officials viewed him with any more sympathy. In a background briefing for the NSC, Director of Central Intelligence Allen W. Dulles said, “We continue to have to deal with Sihanouk who is a difficult character.”