Los Angeles’s SWAT team tested its mettle in 1969 against a local Black Panther militia and again in 1974 during a fierce firefight with the Symbionese Liberation Army, a bizarre but dangerous band of radicals best known for having kidnapped the media heiress Patricia Hearst. Its bona fides thus established, SWAT units spread across the national landscape, romanticized in song and on television.

To these units’ defenders, the need could not be more fundamental: The world is dangerous. Some drug lords have weaponry that would be the envy of small armies; the police cannot possibly take them on with mere handguns. Terrorism lurks as an ever-present threat. And sudden menace demanding a well-armed police response can arise even in the most tranquil places. Indeed, the roster of place names identified principally with gun horrors has grown long: Newtown, Columbine, Aurora, Virginia Tech. On and on.

Not surprisingly, critics of militarized policing have a different take.

Some are troubled by what a retired District of Columbia police sergeant, Bill Donnelly, once belittled as “commando-chic regalia.” With all that armored gear and firepower, Mr. Donnelly wrote to The Washington Post in 1997, “one tends to throw caution to the wind.” Another skeptic is Peter B. Kraska, a professor at Eastern Kentucky University interviewed by Retro Report. Professor Kraska has studied this issue for decades. Originally, he said, SWAT deployment was supposed to be reserved for truly perilous situations — hostage-takings, high-powered shootouts and the like. Now, these teams execute routine warrants in “no-knock” drug raids, bursting into homes with a show of force that often far exceeds the threat to them. The number of such raids has exploded from a few thousand a year in the early 1980s to tens of thousands today. Other critics, like the American Civil Liberties Union, note a stark racial disparity, with blacks and Latinos more likely than whites to be targets.

In the process, relationships between many police departments and the public they serve are intrinsically altered. Officer Friendly has been replaced by someone looking more like G.I. Joe.

The blurring of distinctions between police and the military has troubled people like Lawrence J. Korb, a longtime analyst of national security policies, who was an assistant defense secretary in President Ronald Reagan’s first term. Mr. Korb was not happy when the Reagan administration, in the early 1980s, loosened some restrictions in the Posse Comitatus Act to enable the armed forces to get more involved in the domestic “war on drugs.” His objection was encapsulated in a 1997 interview with The Dallas Morning News. “The military is much more likely to use force of arms because that’s what they’re trained to do,” he said. “The military, to put it bluntly, is trained to vaporize, not Mirandize.”

Over the last two decades, SWAT units have become ever more heavily armed. Under the so-called 1033 Program, named for a provision of the National Defense Authorization Act, the federal government has transferred vast amounts of military equipment — machine guns and ammunition, helicopters, night-vision gear, armored cars — to local police departments. The process accelerated after the Sept. 11 attacks, under both President George W. Bush and President Obama. Inevitably, some people, including police chiefs, have asked if all this amounts to a solution in search of a problem. Take the transfer of MRAPs, the military term for mine-resistant ambush-protected armored vehicles. How many minefields are there on America’s Main Streets?

Also inevitably, mistakes are made. A wrenching example is captured in the Retro Report video, involving a 19-month-old boy who was critically injured in May when a SWAT team in Georgia fired a stun grenade into a house that was the target of a drug raid. The officers were searching for their suspect in the wrong place. Their grenade landed in the infant’s crib.

There is yet another inevitability. After all that happened in Ferguson, a backlash against militarized policing has gained force. In late August, Mr. Obama ordered a review of the equipment-transfer program. Senators said they would hold their own hearings this month. It is much too soon, though, to tell if this longstanding law enforcement strategy is truly about to go thataway.

CLYDE HABERMAN, a regular contributor to Retro Report, has been a reporter, columnist and editorial writer for The New York Times, where he spent nearly 13 years based in Tokyo, Rome and Jerusalem. Subscribe to our newsletter here and follow us on Twitter @RetroReport.

This article first appeared in The New York Times.