The American Civil Liberties Union (ACLU) has launched a nationwide campaign to assess police militarization in the United States. Starting Wednesday, ACLU affiliates in 23 states are sending open records requests to hundreds of state and local police agencies requesting information about their SWAT teams, such as how often and for what reasons they're deployed, what types of weapons they use, how often citizens are injured during SWAT raids, and how they're funded. More affiliates may join the effort in the coming weeks.

Additionally, the affiliates will ask for information about drones, GPS tracking devices, how much military equipment the police agencies have obtained through programs run through the Pentagon and the Department of Homeland Security, and how often and for what purpose state National Guards are participating in enforcement of drug laws.

"We've known for a while now that American neighborhoods are increasingly being policed by cops armed with the weapons and tactics of war," said Kara Dansky, senior counsel at the ACLU's Center for Justice, which is coordinating the investigation. "The aim of this investigation is to find out just how pervasive this is, and to what extent federal funding is incentivizing this trend."

The militarization of America's police forces has been going on for about a generation now. Former Los Angeles Police Chief Daryl Gates first conceived the idea of the SWAT team in the late 1960s, in response to the Watts riots and a few mass shooting incidents for which he thought the police were unprepared. Gates wanted an elite team of specialized cops similar to groups like the Army Rangers or Navy SEALs that could respond to riots, barricades, shootouts, or hostage-takings with more skill and precision than everyday patrol officers.

The concept caught on, particularly after a couple of high-profile, televised confrontations between Gates' SWAT team and a Black Panther holdout in 1969, and then with the Symbionese Liberation Army in 1973. Given the rioting, protests, and general social unrest of the time, Gates' idea quickly grew popular in law enforcement circles, particularly in cities worried about rioting and domestic terrorism.

From Gates' lone team in LA, according to a New York Times investigation, the number of SWAT teams in the U.S. grew to 500 by 1975. By 1982, nearly 60 percent of American cities with 50,000 or more people had a SWAT team.

Throughout those early years, SWAT teams were generally used as Gates had intended. They deployed when there was a suspect, gunman or escaped fugitive who posed an immediate threat to the public, using force to defuse an already violent situation.

By 1995, however, nearly 90 percent of cities with 50,000 or more people had a SWAT team -- and many had several, according to Peter Kraska, a criminologist at Eastern Kentucky University, who in the late 1990s conducted two highly publicized surveys of police departments across the country, and a follow-up survey several years later. Even in smaller towns -- municipalities with 25,000 to 50,000 people -- Kraska found that the number of SWAT teams increased by more than 300 percent between 1984 and 1995. By 2000, 75 percent of those towns also had their own SWAT team.

Kraska estimates that total number of SWAT raids in America jumped from just a few hundred per year in the 1970s, to a few thousand by the early 1980s, to around 50,000 by the mid-2000s.

The vast majority of those raids are to serve warrants on people suspected of nonviolent drug crimes. Police forces were no longer reserving SWAT teams and paramilitary tactics for events that presented an immediate threat to the public. They were now using them mostly as an investigative tool in drug cases, creating violent confrontations with people suspected of nonviolent, consensual crimes.

It was during the Reagan administration that the SWAT-ification of America really began to accelerate. Reagan (and a compliant Congress) passed policies encouraging cooperation and mutual training between the military and police agencies. The president set up joint task forces in which domestic cops and soldiers worked together on anti-drug operations. And, with some help from Congress, he nudged the Pentagon to start loaning or even giving surplus military gear to law enforcement agencies. Subsequent administrations continued all of these policies -- and a number of new ones.

After Reagan, new federal policies provided yet more incentive for militarization. In 1988, Congress created the Byrne grant program, which gives money to local police departments and prosecutors for a number of different criminal justice purposes. But a large portion of Byrne grant money over the years has been earmarked for anti-drug policing. Competition among police agencies for the pool of cash has made anti-drug policing a high priority. And once there was federal cash available for drug busts, drug raids became more common.

Byrne grants also created and funded anti-narcotics multi-jurisdictional task forces. These roving teams of drug cops are often entirely funded with grants and through asset forfeiture, and usually don't report to any single police agency. The poor incentives and lack of real accountability have produced some catastrophic results, like the mass drug raid debacles in Tulia and Hearne, Texas, in the late 1990s.

But politicians love the Byrne grant program. Congressmen get to put out press releases announcing the new half-million dollar grant they've just helped secure for the hometown police department. And everyone gets to look tough on crime.

During the Clinton administration, Congress passed what's now known as the "1033 Program," which formalized and streamlined the Reagan administration's directive to the Pentagon to share surplus military gear with domestic police agencies. Since then, millions of pieces of military equipment designed for use on a battlefield have been transferred to local cops -- SWAT teams and others -- including machine guns, tanks, armored personnel carriers, helicopters, bayonets, and weapons that shoot .50-caliber ammunition. Clinton also created the "Troops to Cops" program, which offered grants to police departments who hired soldiers returning from battle, contributing even further to the militarization of the police force.

Even programs with noble aims have gone awry. Clinton also created the Community-Oriented Policing Services program (COPS), the aim of which was to promote a less confrontational style of policing. But subsequent investigations by publications in Portland, Ore., and Madison, Wis., showed that those grants often went to start or fund SWAT teams. In fact, in interviews with police chiefs as part of his study, Kraska found that many of them believed SWAT raids and militarized policing were perfectly consistent with a community policing approach to crime control.

There hasn't been a major effort to quantify the militarization trend since Kraska's studies in the late 1990s. That's what the ACLU is hoping to do with this investigation.

"You may remember the story from late last year about Pargould, Arkansas, where the mayor and police chief announced that they were going to send the SWAT team out on routine patrols in 'problem neighborhoods' to stop and harass the people who lived in them. After the story made national news, they changed that policy. But how many places is this happening where it isn't making news? That's one of the things we're hoping to find out," Dansky said.

One problem the ACLU may run into is a lack of cooperation from the police agencies it's investigating. Kraska said that when he conducted his surveys in the 1990s, police departments were forthcoming, and even boastful about their SWAT teams. "We had a really high response rate," he said. "But when the reports came out and were critical, and the press coverage was critical, they stopped cooperating." Kraska said the response rate for his follow-up survey dropped off, and that police agencies haven't cooperated with subsequent similar efforts by other criminologists.

In 2009, Maryland passed a SWAT transparency law. It requires every police agency in the state with a SWAT team to provide data twice per year on the number of times the SWAT team is deployed, the reason for the deployment, whether any shots were fired, and whether the raid resulted in criminal charges. The effort to get the law passed was led by Cheye Calvo, the mayor of Berwyn Heights, Md., who was the victim of a highly publicized mistaken raid on his home in which a Prince George's County SWAT team shot and killed his two black Labradors. The bill puts no restrictions on SWAT teams or how they're used. Its only purpose is transparency. Still, it was vigorously opposed by every police agency in the state.

"This is one of the most intrusive things a government can do," Calvo said. "These are government agents, breaking down your door, invading your home. And yet it's all done in secret. In most cases, no one knows what criteria police are using when they decide how to serve a search warrant. There's no transparency, there's no oversight."

"After the law was passed," he continued, "we found out that there are ZIP codes in Maryland where every search warrant is served by a SWAT team. I mean, even if you don't care about civil liberties, in some places less than half of these raids result in so much as a single arrest. So you're conducting these dangerous, volatile raids, you're terrifying people and putting them at risk, and you're serving no law enforcement purpose."

Neither Kraska nor Calvo are optimistic that the ACLU will get much cooperation. "I'd imagine they'll mostly be declined," Calvo said.

"My experience is that they'll have a very difficult time getting comprehensive, forthright information," Kraska said. "If the goal here is to impose some transparency, you have to understand, that's not what the SWAT industry wants."

Dansky said the ACLU is prepared to go to court to get access to the information it's seeking. "We don't expect we'll need to for information on the equipment these police agencies have received from the Defense Department or Homeland Security," she said. "But if we need to challenge these departments on the information about their SWAT teams, we'll do that. And if these police agencies do refuse to release this public information to our affiliates, that in itself is something the public should know."

The National Sheriffs Association and the National Association of Chiefs of Police did not respond to HuffPost requests for comment. But Mark Lomax, executive director of the National Tactical Officers Association -- a trade association and lobbying group for SWAT teams -- said he has no problem with releasing the information the ACLU is requesting.

"There's nothing to hide here," Lomax said. "The only stipulations I'd add is that I'd oppose releasing information about the specific tactics a police department uses. There also might be legal reasons for not releasing information -- if cases are in litigation, for example. I'd also be concerned about how the data is used. You can make information like that say whatever you want it to. But in general I wouldn't have a problem with making it available."

It's almost certain that if the police agencies cooperate, the ACLU will find that the militarization trend has accelerated since Kraska's studies more than a decade ago. All of the policies, incentives and funding mechanisms that were driving the trend then are still in effect now. And most of them have grown in size and scope.

The George W. Bush administration actually began scaling down the Byrne and COPS programs in the early 2000s, part of a general strategy of leaving law enforcement to states and localities. But the Obama administration has since resurrected both programs. The Byrne program got a $2 billion surge in funding as part of the 2009 American Recovery and Reinvestment Act, by far the largest budget in the program's 25-year history. Obama also gave the COPS program $1.55 billion that same year, a 250 percent increase over its 2008 budget, and again the largest budget in the program's history. Vice President Joe Biden had championed both programs during his time in the Senate.

The Pentagon's 1033 program has also exploded under Obama. In the program's monthly newsletter (Motto: "From Warfighter to Crimefighter"), its director announced in October 2011 that his office had given away a record $500 million in military gear in fiscal year 2011, which he noted, "passes the previous mark by several hundred million dollars." He added, "I believe we can exceed that in FY 12.”

Then there are the Department of Homeland Security's anti-terrorism grants. The Center for Investigative Reporting found in a 2011 investigation that since 2001, DHS has given out more than $34 billion in grants to police departments across the country, many of which have been used to purchase military-grade guns, tanks, armor, and armored personnel carriers. The grants have gone to such unlikely terrorism targets as Fargo, N.D.; Canyon County, Idaho; and Tuscaloosa, Ala.

In the tiny town of Keene, N.H.,, the citizens protested plans to purchase a Lenco Bearcat armored personnel carrier with a DHS grant. One resident told HuffPost last year, "Keene is a beautiful place. It's gorgeous, and it's safe, and we love it here. We just don't want to live in the kind of place where there's an armored personnel carrier parked outside of City Hall ... It's just not who we are."

They succeeded only in delaying the purchase by a few months. Keene now has a Bearcat. To town officials, it was a no-brainer. Keene was getting a $400,000 vehicle from the federal government, essentially for free. Why wouldn't it accept?

"From all indications, I would think the DHS grants and increased federal funding could only speed up the militarization process," Kraska said. "And now you have an entire industry that has sprung up just to take advantage of those grants -- and to lobby to make sure they keep coming."

Like the Maryland law, the ACLU program is really only seeking information. Once it gets the information, Dansky said the organization will analyze the figures and recommend policies to minimize the effects of police militarization on civil liberties. "We're also concerned that these tactics are disproportionately used against poor people, and in communities of color," Dansky said. "And SWAT is really only part of it. The effects of militarization also happen beyond and outside of just an increase in SWAT deployments."

Of course, you can always gather information showing a troubling rise in the use of military weapons and tactics among domestic police agencies, make sensible recommendations for reform, and get no interest at all from politicians and policymakers. Kraska's studies in the late 1990s, and subsequent media reports, did nothing to stem the increased militarization of the police.

And in Maryland, the transparency law has shown that police departments in the state are using SWAT tactics in precisely the ways critics have claimed: to break into homes to serve warrants on people suspected of low-level drug crimes. Many times, they're not even finding enough contraband to make an arrest. Yet there haven't been any calls in the state to reform the way SWAT teams are used.

"I wish the ACLU success," Calvo said. "And I suspect that once they force the police agencies to cooperate, they'll find that this problem is even more dramatic and pronounced than most people know. But then the question is, now what? Even if you can show that people are being victimized and terrorized by these tactics -- and to no good end -- if no one cares, then what does it matter?"

HuffPost investigative reporter Radley Balko is author of the forthcoming book Rise of the Warrior Cop: The Militarization of America's Police Forces.

This story appears in Issue 42 of our weekly iPad magazine, Huffington, in the iTunes App store, available Friday, March 29.