By 1975, there were over 500 SWAT teams throughout the country. However, it was through President Richard Nixon’s notorious ‘War on Drugs’ that the migration of military technology and tactics to domestic law enforcement took off. A decade later in 1981, the U.S. Congress passed the Military Cooperation with Civilian Law Enforcement Agencies Act, which allowed the American military to cooperate with law enforcement in several different scenarios, including counter-narcotics operations, civil disturbances, special security operations and threats of terrorism.

As a result, police were given access to military-grade equipment, as well as accompanying training by armed forces personnel. By 1995, nearly 90 per cent of all American cities with more than 50,000 residents had a paramilitarized police unit.

The 1981 law represented a key moment in American history. Up to that point, a clear line separated the country’s military and police through the Posse Comitatus Act, an 1878 law that prohibited the military from exercising law enforcement powers on non-federal property: in other words, the military could not be involved in domestic policing. Congress passed Posse Comitatus as an explicit response to the use of Union troops to occupy the former Confederate States of American following the end of the Civil War.

The Military Grip on US Policing