WASHINGTON — FERGUSON, Mo., has become a virtual war zone. In the wake of the shooting of an unarmed black teenager, Michael Brown, outsize armored vehicles have lined streets and tear gas has filled the air. Officers dressed in camouflage uniforms from Ferguson’s 53-person police force have pointed M-16s at the very citizens they are sworn to protect and serve.

The police response has shocked America. The escalating tension in this town of 21,200 people between a largely white police department and a majority African-American community is a central part of the crisis, but the militarization of the police is a dimension of the story that has national implications.

Ferguson’s police force got equipped this way thanks to the Pentagon, and it’s happening all over the country. The Department of Defense provides military-grade weapons and equipment to local law enforcement agencies through the 1033 program, enacted by Congress in 1997 to expand the practice of dispensing extra military gear. Due to the defense industry’s bloated contracts, there is a huge surplus. To date, the Pentagon has donated military equipment worth more than $4 billion to local law enforcement agencies. And the giving goes on, to police forces in all 50 states in the union.

Ferguson’s police department is just one recipient; small towns all over America are now the proud owners of “MRAP” armored vehicles. The largess has gotten so out of hand that a congressman, Hank C. Johnson, is introducing a bill to block the 1033 handouts.