Although the Phoenix program borrowed some aspects of the Kien Hoa model, he concluded that it placed too much emphasis on the use of force and not enough on the mobilization of the population. As a result, Mr. Chau and his American friends came to see Phoenix as a “perversion” of his original ideas. Mr. Chau has presented this interpretation in interviews, in his 2012 English-language memoir, and in the recent documentary film “The Vietnam War” by Ken Burns and Lynn Novick.

But what did Mr. Chau actually accomplish in Kien Hoa? His American supporters often cited official statistics to demonstrate his success: During his first year as province chief, the estimates of the number of civilians living in government-controlled areas of the province rose from 80,000 to 220,000 (out of a total population of more than half a million). Yet Mr. Chau himself often noted that such gains counted for very little if local residents could not be persuaded to identify with the government and its claims to national sovereignty — a goal that proved exceedingly difficult in South Vietnam during the mid-1960s. The fleeting quality of Mr. Chau’s achievements was revealed after his departure from Kien Hoa, when Communist forces quickly recovered most of the territory and population they had lost.

Mr. Chau’s most tangible achievement in Kien Hoa was the Census-Grievance program. As a C.I.A. historian later noted, the program proved an effective means of generating actionable intelligence on enemy operatives and forces. But its effectiveness derived less from the winning of popular support than from its surveillance of the population.

Indeed, the program did not merely collect intelligence on the “Vietcong infrastructure.” It compiled detailed information on every resident of every hamlet and village in which the program operated — information that included data about kinship ties, political and religious affiliations and property ownership. As Mr. Chau acknowledged, this information was often used to pressure families and entire communities to comply with the government’s directives. In this regard, the program was less benign and more coercive than its promoters acknowledged.

The use of the Counter-Terror teams in Kien Hoa also sometimes failed to conform to the high-minded principles that Mr. Chau preached. By targeting specific Communist cadres for “neutralization,” the program increased the military and psychological pressure on the enemy. Communist commanders responded by offering special bounties to any of their men who killed a Counter-Terror team member. The struggle between the two sides quickly devolved into community-level internecine warfare in which Mr. Chau’s promise to use violence only as a last resort often went by the boards: When Communist propagandists distributed fliers celebrating a guerrilla sniper who killed an American military adviser in Kien Hoa, Mr. Chau ordered a Counter-Terror team to infiltrate the enemy-controlled hamlet where the sniper lived. Team members killed the sniper by tossing grenades into his house while he slept.

Critics of American counterinsurgency practices in Vietnam would most likely treat the sniper story as proof that Mr. Chau’s activities in Kien Hoa constituted an assassination program, pure and simple. He and his defenders might reply that such killings were necessary and were justified by the Communists’ use of targeted killings, and that his occasional deployment of such tactics should be evaluated in the context of his broader efforts to win “hearts and minds.” But both of these arguments discount critical elements of counterinsurgency warfare as it was practiced in Vietnam.

Mr. Chau did not propose to defeat the Communists in Kien Hoa merely by assassinating them. He created the Census-Grievance teams specifically as a means to enlist the population in the fight against the enemy. However, the process by which he proposed to ensure the cooperation of villagers was not one that depended on gaining their consent or willing participation. The Census-Grievance teams provided the government with a way to impose a system of surveillance and control over entire communities and to extract intelligence from individual residents. While Mr. Chau hoped that residents would provide this intelligence voluntarily, his overriding goal was to acquire the information needed to expose and destroy the enemy’s clandestine networks. Moreover, while the pursuit of this goal included efforts to capture enemy operatives or to persuade them to surrender, it also involved plenty of intimidation and deadly force — including some assassinations. In all of these aspects, the model that Mr. Chau devised in Kien Hoa bore more than a passing resemblance to the later Phoenix program.