In February 1966, Senator Robert Byrd penned an article for the Police Chief, the monthly magazine of the International Association of Chiefs of Police. A conservative Democrat from West Virginia, notorious for his staunch opposition to the Civil Rights Movement, Byrd had no experience whatsoever as a cop. But he took this chance to engage the police community during a period of apparent national and international crisis. In Vietnam, the US military was failing in its campaign against the communist-led insurgency. In the United States, authorities were bracing for another summer of black rebellions in US cities.

Fearing revolt at home and abroad, Byrd cast his sympathies with those whose job it was to maintain order: cops and soldiers. As he put it, police officers in US cities “have a great deal of sympathy with the troops in Vietnam because they fight a similar type of dirty war in which the enemy is forever striking from the shadows. The police know guerrilla warfare because they fight it day in and day out with criminals on American streets.” In the minds of Byrd and others, the line between different arenas and modes of state power vanished. Policing meant counterinsurgency. Counterinsurgency meant policing.

Stuart Schrader’s Badges Without Borders explains how and why policing and counterinsurgency morphed into each other. Focused on the peak years of the Cold War, roughly the 1950s through the early 1970s, his analysis ranges across the globe, tracing the complex connections that linked US crime-fighters to their allies abroad. Some were police chiefs or policymakers, others military officials or academics. Working across institutional divides and international borders, they honed a model of policing that sought, above all, to maintain order.

This is a messy story, since those connections flowed in multiple directions simultaneously. Cops in US cities used technologies, such as the handheld radio and CS gas, that had first been deployed in war zones abroad. US soldiers in Vietnam and elsewhere drew upon techniques police had pioneered in New York, Kansas City, and Los Angeles to transform local constabularies into effective and efficient forces. US-based police training academies produced thousands of graduates who carried with them lessons American cops had learned at home. Meanwhile, in official circles, policymakers and academics tended to conflate — and often exaggerate — the supposed threat of mass crime and communism, while urging the same solutions for both.

To distill meaning from this messiness, Schrader has assembled and interrogated a vast archive. He’s examined legislation and official documents, speeches and television programs, police manuals and training materials, corporate advertisements and think-tank theses. Drawing on these sources, Schrader makes clear that US policing cannot be understood apart from the United States’ Cold War crusade to thwart leftist insurgencies.

Other scholars have tackled this topic. Historian Jeremy Kuzmarov’s Modernizing Repression, for instance, explained how US policymakers used police training for Cold War aims, launching far-reaching efforts to modernize and militarize the constabularies of dozens of foreign countries. Kuzmarov’s story was about power projection. Simply put, US police and policymakers exported repression around the world.

But Schrader is after something else. He’s interested not so much in the projection of American policing techniques, but instead in their circulation. Throughout the book, he holds the United States in constant view alongside those far-flung locales where American policing strategies migrated. His story documents how domestic anti-crime policies evolved in a transnational sphere of exchange and collaboration, revealing surprising links between domestic and overseas developments.

The key figure in Badges Without Borders is Byron Engle, who spent nearly four decades guiding police in the United States and dozens of other countries. Born in 1910 in the hamlet of Buffalo, Missouri, he joined the Kansas City police force in 1940. Engle was inspired by police reformers in other cities and aimed to replicate their success in the Kansas City force, which had long been bound up with political patronage and corruption. He helped institute new standards for hiring and training officers, while traveling the country to learn cutting-edge techniques from other police departments as well as the FBI. Before long he was a renowned expert in riot control, among other specialties.

Engle’s professional connections propelled his rise within the national policing community. By 1946, as US policymakers sought to remake their wartime enemies into stable allies, Engle shipped off to Japan, his first tour abroad. Joining General Douglas MacArthur’s command, Engle worked to rebuild and reform Japan’s police forces. He drew upon his experience in Kansas City, stressing professionalism and technological development. By the end of his tour, Japan’s police “dressed like officers back home.” They carried nightsticks and used handcuffs instead of the rope bindings Japanese officers had long employed. In Engle’s eyes, Japan was the “best laboratory that anyone interested in organization and administration could have been involved in.”

Other laboratories soon emerged. Engle circulated between Kansas City, Washington DC, Japan, the Dominican Republic, Turkey, and elsewhere. These travels transformed his view of policing. The task of police, in his eyes, wasn’t simply to catch common criminals. Rather, its main goal should be protecting the state from radical political challenges, especially those of the Left. As far as Engle was concerned, crime and communism were essentially the same thing, since both posed deep challenges to the established order. Leftists encouraged lawbreaking while criminals subverted society, allowing leftists to gain ground.

Counterinsurgency offered the solution to each problem. In 1962, Engle accepted a new post as the director of the Office of Public Safety (OPS). Part of the US Agency for International Development (USAID), created by the Kennedy administration in 1962, the OPS would become the nerve center for US-sponsored police training across the globe. It would also play a key role in driving domestic “tough on crime” legislation.

Under Engle’s helm, the OPS served as the “first line of defense” against subversion and crime. From 1962 until 1974, when the OPS closed up shop, it sponsored training missions in at least fifty-two countries in Asia, Africa, Latin America, and the Middle East. Many more nations sent police officers to the United States to study with the FBI, CIA, and the International Police Academy. All told, Schrader notes, US public safety assistance reached over a million police officers around the world.

Wherever the tentacles of the OPS spread, the mission was the same. US agents and their overseas allies joined together to build professionalized police forces that would deal with crime and subversion before they spiraled into large-scale insurgencies that threatened the internal security of overseas allies. Maintaining order abroad would, in turn, defend and promote US dominance on the world stage.

For many, this was the cheapest and yet most efficient response to the problem of communism in the Global South. Sending in troops meant killing people and bombing villages. It meant disrupting the social order. But policing was constructive, not destructive. Regularized and routinized, policing could shape how people behaved indirectly. As one US official put it, police aimed to “restore order, not destroy the enemy.”

As such, police would play a vital role in the process of modernization urged by Walt Whitman Rostow and developmentalist theorists. If you wanted to defeat communism, Rostow argued, you had to ensure that poor countries had enough time to transition their economies to the point of “takeoff,” when they would inexorably mature into stable capitalist societies. Before that could happen, however, the state needed to dismantle leftist forces who might channel popular discontent into popular insurgency. Simply put, the state needed security. Crime, in this view, appeared as a political act, even when it was entirely unconnected from any kind of formal politics. Criminals created the disorder that bred leftist insurgencies.

Even though the OPS prided itself on professionalism, it tended to promote extralegal violence. In Uruguay, OPS officers urged their counterparts to torture, intimidate, execute, and disappear suspected subversives. In Vietnam, OPS agents worked with the CIA’s Phoenix Program, an assassination operation that killed more than twenty thousand people and ran a torture facility at an island prison. They also joined the US Army’s CORDS program, a rural pacification effort that swelled the ranks of Vietnam’s national police and pressed them into counterinsurgency campaigns in the countryside.

Similar stories unfolded elsewhere. In Guatemala, OPS agents organized a counterinsurgency unit that launched Operación Limpieza (“Operation Cleanup”) in 1966. Police and paramilitary forces disappeared and executed hundreds of labor organizers and peasant leaders, dumping many into the ocean. When their bodies washed up on the coast, adviser John Longon, a former cop from Oklahoma, explained that these things “just happen.”

As OPS sought counterinsurgency through crime control, and vice versa, US policymakers borrowed those strategies to counter domestic challenges. The most important were the dozens of rebellions that convulsed Newark, Los Angeles, Harlem, Detroit, and other major cities between 1964 and 1968. Cribbing from the script that the OPS had written abroad, lawmakers and crime control experts explained that the unrest in the United States spurred and escalated political challenges to the nation’s existing social order. The riots were, in other words, domestic insurgencies — and they demanded the same pacification response that the OPS had honed abroad.

Through the 1968 Omnibus Crime Control and Safe Streets Act and other pieces of legislation, lawmakers extracted key tenets of counterinsurgency overseas and shot them into the domestic sphere. Independently of Washington, local police departments had long operated extralegal intelligence divisions — so-called Red Squads and the like — designed to infiltrate and disrupt leftist organizations and perceived political opponents. For President Lyndon Johnson and his advisors, the “modernization of domestic policing” was “a companion to, and insurance for, the Great Society.”

In the minds of many officials, cops had been crucial to the economic development of poor countries. So it made sense for them to play a similar role in federal anti-poverty initiatives. Like their overseas counterparts, domestic police reformers stressed training, professionalization, and technological advance. And their goal was essentially the same: insulate the existing order from radical challenges so that economic development could proceed gradually. They would pacify the insurgents.

Yet when Great Society programs faltered — or were undermined by their conservative opponents — the focus on policing remained. More than that, it became the state’s most enduring response to the problems facing poor and working-class communities, particularly those of color.

The Office of Public Safety, one of the main conduits for US police assistance in the Cold War, closed in 1974. Yet its mission lived on. As policing and punishment have swallowed larger and larger swaths of American life since the 1970s, US cops have continued to press their crusade abroad. They’ve migrated through a growing number of agencies and departments such as the Drug Enforcement Agency, which straddles the divide between overseas and domestic policing.

The end of the Cold War prompted US officials to shift their concern from communism to terrorism, funneling millions of dollars around the world to defeat Islamist radicals. In rhetoric and deed, American leaders have blurred the line between policing and war-fighting so much that it’s hardly visible anymore. Meanwhile, local and state police forces have used federal funds to purchase the very same military technology that forces have used in Iraq and Afghanistan. When Americans encounter cops, they also encounter armored personnel carriers, M4 rifles, noise-based crowd control devices, rubber-coated metal pellets, and tear gas.

Today, movements for social justice are working to reconstruct or abolish the US criminal justice system as it stands. But a true reckoning with the costs and consequences of mass incarceration, police militarization, and racial disparities in law enforcement cannot focus on the United States alone. Because American policing has shaped and been shaped by forces that transcended the nation-state, our ability to transform this globe-spanning system depends on us knowing how and why it came into being.

Badges Without Borders is a good place to start looking for answers.