Counterinsurgency’s once-vocal American advocates have gone silent. This group once touted “COIN” as the political-military-social strategy for neutralizing irregular, armed challenges to friendly regimes or occupying forces. But the unsatisfactory outcome in Iraq, which is increasingly an Iranian satrapy, and the resiliency of the Afghan Taliban, despite the commitment of billions of dollars and loss of lives, have helped quiet those policymakers, military officers and analysts.

In her introduction to the 2007 edition of the influential U.S. Army-Marine Corps COIN field manual, Harvard’s Sarah Sewell touted COIN as a form of armed social work aimed at promoting what she called “a more holistic form of human security.” It is a testament to the oddly romantic appeal of the doctrine that such naïve notions went largely unrecognized and unchallenged at the time. (Recent studies by scholars such as Douglas Porch, David Martin Jones and David Anderson are welcome correctives to the overweening claims made by counterinsurgency enthusiasts in and out of uniform.)

As the current counterinsurgency era draws to a close, the time is ripe for further assessments of the COIN’s costs and consequences. One important area of inquiry is the its impact on the countries that have conducted protracted counterinsurgency campaigns. The United States during the Vietnam era offers a particularly rich case study.

During counterinsurgency’s heyday in the 1960s, COIN notions percolated throughout the U.S. national security establishment. What appeared to be brilliantly effective against communist guerrillas abroad also seemed to hold great promise for dealing with civil unrest at home. The popular press, before it soured on Vietnam, served as a transmission belt for such notions. One nationally syndicated author, writing in 1965, described the counterguerrilla exploits of General Edward Lansdale in the Philippines and Vietnam, and insisted that “our ghettos, too, need a Lansdale. They need a whole army of Lansdales.”

When viewed through the COIN lens, America’s cities looked remarkably like the insurgent-infested hamlets of South Vietnam. Fortunately, the U.S. government never waged domestic counterinsurgency. But some civilian policymakers, military officers and academic specialists contemplated it. COIN provided the mental apparatus that enabled them to view rioting fellow citizens as part of a global threat stretching from Southeast Asia to Los Angeles, Detroit and Newark.

The mid-1960s were a period of intense and protracted political violence—the most severe since the Civil War. Between 1964 and 1968, 329 major riots took place in 257 cities, according to one estimate. In the perfervid political atmosphere of the time, some on the extreme political left championed ghetto unrest as black resistance to white “occupation” and internal colonialism. But the belief that these “uprisings” were revolutionary insurrections was hardly confined to radicals.

Apocalyptic visions of black, urban-based revolution also circulated among mainstream policy experts. Abetted by social science, it was possible to see fighters in dripping Asian jungles, rebellious students tearing up French paving blocks, and Molotov-cocktail throwing Newark agitators as part of a seamless whole. Prominent theorists who had developed tools for predicting and containing violent revolution in the global South increasingly turned their attention to domestic U.S. instability. RAND’s Guy Pauker warned in 1969 that African-American veterans returning from Southeast Asia to life in U.S. ghettos could form the “military trained cadres of a black terrorist movement.” A “systems approach” to COIN in Vietnam was equally applicable to urban disorders and growing campus unrest, according to Nathan Leites and Charles Wolf, Jr., also at RAND.

The notion that violent revolution was unfolding at home gained currency among influential law-enforcement and military officers. Predictably, FBI director J. Edgar Hoover detected the subversive influence of U.S. communists and what the bureau termed “representatives of unfriendly or hostile countries.” Daryl Gates, who went on to serve as chief of the Los Angeles Police Department, wrote in his memoirs that the 1965 Watts riots led him to conclude that “the streets of America had become a foreign country.” Following Watts, Gates became a keen student of counterinsurgency in Vietnam and sought operational advice from Marines at a nearby base.

In an article for U.S. News & World Report, a retired U.S. army colonel claimed that the dangers within American ghettos were greater than threats emanating from abroad. “Urban guerrillas of the future,” he warned, “can be organized to such a degree that their defeat would require the direct application of military power.” At the Pentagon, some senior army officers were increasingly alarmed by domestic turmoil. Major General William P. Yarborough, the army’s assistant chief of staff for intelligence, reportedly told subordinates during the 1968 Detroit riot to “get out your counterinsurgency manuals. We have an insurgency on our hands.” Under Yarborough’s direction, the army stepped up its surveillance of ghetto residents, sending more than one thousand plainclothes agents deep into the nation’s cities to identify agitators, collaborators and hotspots.

As the nation’s urban areas smoldered, police girded themselves for urban combat. The armed forces supplied training, equipment, and weapons. Army research and development centers identified nonlethal weapons and technology that might prove useful in the control of domestic unrest. The Limited War Laboratory at Aberdeen Proving Ground in Maryland identified weapons and riot-control agents ranging from the banal to the bizarre: “itch-inducing” powders, pain-producing sprays, “instant banana peel,” “Turb-a-Fog” tear gas dispensers, and “sticky aerosols/jets” designed to attract an “insect swarm.”

Ultimately, America never waged counterinsurgency at home. Some on the far left would continue to claim that the U.S. government had instituted COIN-inspired measures like population control, targeted killings and psychological operations—but such charges were fanciful. Any lingering rationales for domestic COIN evaporated during the early 1970s as direct U.S. involvement in Vietnam wound down, violent antiwar protests stopped, and episodes of ghetto unrest declined. Public exposure of U.S. Army domestic spying operations undercut whatever enthusiasm the military had for operations at home. More broadly, COIN lost its intellectual and operational luster, a casualty of the U.S. debacle in Southeast Asia.

But during the mid-2000s, the COIN romance was rekindled. During the latter half of the decade, as counterinsurgency in Iraq appeared to be paying rich dividends, the passion became overheated. As during the Vietnam period, techniques for quelling insurrection abroad seemed to be applicable at home. The threat this time was not urban insurrection and revolution fomented by black nationalists, but drugs, drug traffickers and ethnic gangs. Reflecting a widespread moral panic over these problems, one prominent military analyst warned in 2008 that the gangs represented an incipient insurgency that threatened suburbs and cities across the country. The United States, he concluded, was “increasingly vulnerable to civil violence and attack from within.”

Counterinsurgency expertise, developed through hard campaigning in Central America in the 1980s and, more recently, in Iraq and Afghanistan, was readily available to civilian officials. In 2009, city officials turned to COIN experts at the nearby Naval Postgraduate School for countergang advice. According to a former Special Forces officer teaching at the school, there is “significant overlap with how you deal with insurgencies and how you deal with cities that are under siege from gangs.”

Today, the romance of COIN has cooled once again. It seems unlikely that government officials will look to counterinsurgency for answers to domestic challenges—at least not anytime soon. But the lure of COIN is persistent, if episodic. And new developments—such as the spillover of gang violence from Mexico into the United States—may yet again reawaken enthusiasm for domestic COIN.

William Rosenau is a senior research scientist at CNA Strategic Studies.