On Thursday, Missouri Gov. Jay Nixon ordered the National Guard out of Ferguson, Mo., saying the nighttime violence and looting that spun off from public protests over the Aug. 9 shooting of Michael Brown had susbsided. But the streets of Ferguson, near the street where the unarmed Brown was shot and killed in a confrontation with police officer Darren Wilson, had the look and feel of a military occupation before the National Guard arrived.

Soon after the peaceful daytime protests became violent at night, Ferguson police showed up on the streets with military-style Humvees and sniper rifles. The image of a military confrontation struck many Americans as an overreach by police. The familiar idea that local police are dedicated to “protect and serve” was overshadowed by the military equipment suggesting war rather than protection.

Most Americans, seeing the amored vehicles and military sniper rifles trained on protestors, had no idea that suburban police departments had access to this type of military gear. In Congress, the images sparked a debate over the militarization of police, which can be traced to 1990, when Congress authorized the Pentagon to offer hand-me-down weapons and equipment to local police to help fight the war on drugs. The war on terror, launched after the Sept. 11, 2001 terrorist attacks, accelerated the movement of military equipment to local police forces around the country.

It might be reasonable to see police in New York City, Los Angeles or Chicago needing some military-style equipment to deal with a terror-related attack or other sort of major incident. But it’s hard to see why a suburban police department, such as the force in Ferguson, needs sniper rifles and armored Humvees.

The question of putting military equipment in the hands of police will be addressed next month in Congress. Missouri’s Sen. Claire McCaskill will lead the hearings as chair of the Financial and Contracting Oversight Committee. McCaskill, like several others, said that the war-zone gear had become part of the problem in Ferguson instead of part of a solution.

The general view is that the military images sent the wrong message to protestors in Ferguson and actually increased tensions rather than working to restore calm.

The New York Times requested — and received — from the Pentagon a database of all military equipment transferred to local police forces. Applying the data to a map of the United States illustrates the fact that the vast majority of counties received some sort of military gear from the Pentagon. Items tracked ranged from sniper rifles and night-vision goggles to body armor, grenade launchers, vehicles and even helicopters.

Butler County, according to the Times data, did not receive any of the hand-me-down military hardware. But most in the state did. For example, Armstrong County got two assault rifles, while Beaver County received five. The Times graphic shows rural Venango County as receiving 12 assault rifles and one armored vehicle.

In the middle of South Dakota, Hughes County is listed as the recipient of 310 assualt rifles, 16 night vision pieces and three armored vehicles. Four hundred miles to the north, Grand Forks, N.D., is shown as receiving 18 assault rifles and two grenade launchers.

These statistics raise obvious questions. What justification did the Pentagon require before sending out assault rifles, grenade launchers and armored vehicles to small towns and rural counties? Did the trickle-down program make it easier for the Pentagon to buy new weapons, despite the gear being transferred to police departments across the U.S. still considered to be in good working condition?

Maybe there are good reasons for all this military hardware to now be in the hands of local police departments, but maybe not.

It could be that the military-weapons transfer effort was a well-intentioned federal program that got out of hand and had little oversight.

For that reason, Sen. McCaskill’s review next month will be welcome — and could prove very interesting.

Along with issues of race, poverty and apparent unequal treatment by some police forces, the Ferguson tensions should spark a national discussion about the wisdom and implications of so much military hardware being given to local police departments in every state of the country.