Ambassador Bunker warned Nguyen Cao Ky against a coup in 1967

By Desmond Okafor · August 17, 2026

South Vietnamese civilians lived under a precarious military junta while US diplomats spent 1967 suppressing threats of a coup kept under "Secret; Exdis" classification.

The civilians of South Vietnam lived in a state of permanent fragility, their lives subject to the whims of a military junta. Every disagreement between the nation's generals carried the risk of a coup, a cycle of instability that cost thousands their lives and erased the possibility of genuine self-governance.

In the summer of 1967, that fragility was managed by an American embassy that viewed the sovereign government of South Vietnam as a series of personality clashes to be moderated. A telegram from the Embassy in Vietnam to the Department of State, dated July 29, 1967, and marked "Secret; Exdis," captures a moment where the facade of democratic transition nearly cracked under the weight of military ambition.

"a collegiate form of control"

Ambassador Ellsworth Bunker and a colleague named Calhoun met with Bui Diem on July 28 to gauge the temperature of the relationship between the two most powerful men in the country: Nguyen Van Thieu and Nguyen Cao Ky. According to the record, Bui Diem suggested that while the personal relationship between the two was "improving" and they were cooperating on their campaign, the stability was a surface-level illusion.

Bui Diem warned Bunker that he "foresaw some future problems" once a new government was formed. The core of the issue was the emerging "collegiate form of control" among the top military leadership. In the eyes of the junta, the election was not a move toward civilian rule, but a rebranding of military authority. The generals intended to maintain this collective grip on power regardless of who officially held the title of president.

For the people of Saigon, this meant the "Constitution" mentioned in the telegram was less a legal framework and more a piece of diplomatic theater. Bui Diem expressed worry about how this military consensus would impact "civilian-military cooperation," but the record makes it clear that the military was not interested in cooperation—it was interested in control.

Saigon, July 29, 1967

The telegram documents a desperate attempt by the US embassy to spell out a "division of responsibilities" between Thieu and Ky. The Americans were not acting as observers of a foreign election; they were architects of a power-sharing agreement between two rivals who viewed the state as their personal fiefdom.

While the State Department was concerned with the "way things were going," the reality on the ground was a government led by men like Nguyen Cao Ky, a military officer and former prime minister whose public image was as loud as his ambitions. The public record notes that Ky would eventually serve as vice president to his bitter rival, Thieu, in a nominally civilian administration. But the private cables show that this arrangement was born not of political maturity, but of American pressure to avoid a total collapse of the regime.

"no such action as a coup"

The most volatile detail of the exchange is buried in a footnote to the telegram. Ambassador Bunker confronted Bui Diem regarding an "offhand remark" made by Ky. The Air Force chief had suggested that he might resort to a coup if the upcoming elections were deemed unfair.

Bunker’s response was not one of diplomatic curiosity, but of stern command. He told Bui Diem that the United States "could not contemplate any such action as a coup."

The phrasing is telling. The US was not concerned with whether the elections were actually fair, or whether the Vietnamese people were being denied their voice. The concern was the "action" of the coup itself—the disruption of the American timeline and the potential for a chaotic transition that would complicate the war effort. The "fairness" of the vote was secondary to the predictability of the regime.

The record leaves a gaping silence on how Ky reacted to this warning or what specific threats he had made to ensure his own survival. It merely notes the sternness of the American ambassador. Following these tensions, Ky did not launch a coup, but remained tethered to Thieu in a marriage of convenience that lasted until his retirement from politics in 1971.