WASHINGTON — Police SWAT teams are forcing their way into homes, often using explosive devices, simply to serve drug possession search warrants in tactics that a leading civil rights groups said on Tuesday treated civilians as wartime enemies.

The American Civil Liberties Union (ACLU) said federal government programs that armed police “with the weapons and tactics of war” had led forces across the United States to become unnecessarily and dangerously militarized.

“The use of hyper-aggressive tools and tactics results in tragedy for civilians and police officers, escalates the risk of needless violence, destroys property and undermines individual liberties,” the ACLU said in a report.

It said police forces set up special weapons and tactics (SWAT) units initially to face emergencies such as hostage situations and active-shooter scenarios.

But after studying more than 800 SWAT deployments conducted by 20 law enforcement agencies between 2011-2012, the ACLU said the specialized teams had moved away from that original role and were increasingly used to search people’s homes for drugs.

It said the raids were often violent, involving 20 or more officers armed with assault rifles and stun grenades, breaking down doors and windows, and screaming at occupants to get on the floor. It said children were present on numerous occasions.

The ACLU said the militarization of policing was also evident in police training that it said encouraged officers to adopt a “warrior” mentality – something it said was reinforced by the use of equipment such as battering rams, flashbang grenades, and armored personnel carriers.

It said the shift in culture was partly driven by U.S. Supreme Court rulings that gave police increased authority to force their way into homes, often in narcotics probes.

More than three-quarters of the incidents it reviewed involved the use of a SWAT team to search someone’s home, and more than 60 percent involved searches for drugs.

Of the incidents in which officers believed a weapon would be present, posing a threat to them, a firearm was found at the scene only 35 percent of the time.