Baltimore Riot Police
Police officers in riot gear block Guilford Avenue near City Hall in Baltimore, on May 1, 2015, the day that the Baltimore city state's attorney announced that six police officers involved in the arrest of Freddie Gray face criminal charges. On Monday, the Obama administration moved to limit the use of military equipment by U.S. police forces. Reuters/Sait Serkan Gurbuz

Police militarization in the U.S. was thrust into the national conversation nearly a year ago, following the death of Michael Brown in Ferguson, Missouri. But it wasn't until Monday, when President Barack Obama announced a plan to limit the use of military equipment by local police forces, that tangible action had been seen on it.

Experts say there is a long history of militarization of the police, dating back to race riots that broke out in a handful of U.S. cities in the 1950s and 1960s. Some believe that the seeming success of SWAT teams deployed to curtail the 1965 Watts Riots -- a six-day race riot sparked by conflicts with the Los Angeles police that resulted in 34 deaths -- gave way to the trend of arming and equipping police forces with battlefield weapons. A massive expansion of police militarization came after the Sept. 11, 2001, terrorist attacks in New York City and Washington, where law enforcement agencies stressed the readiness of local police forces, in the event of another domestic terror incident.

Baltimore National Guard
A man gestures as military vehicles drive on the streets of Baltimore, Maryland, on May 1, 2015. Reuters/Lucas Jackson

Bonnie Bertram, who chronicled the rise of SWAT teams in a investigation for Retro Report last year, said tactical units were quickly put into place following the race riots, but over time their deployment among police forces shifted away from civil unrest. “[During] this 50 years of evolution, they really changed from their initial intent," Bertram told the Huffington Post. “They were designed to deal with very violent confrontations starting primarily in the 1980s when Ronald Reagan was ramping up the drug war and these … federal grants [were] coming in to take military surplus goods and transfer them to local police forces. Those two things sort of coalesced.”

Oscar Grant Riot
Law enforcement officers form a line during a protest against the verdict in the case of Bay Area Rapid Transit (BART) officer Johannes Mehserle, who killed Oscar Grant, a unarmed black resident, in Oakland, California, on July 8, 2010. Reuters/Robert Galbraith

Bertram also said that SWAT team have sprung up in small cities, where police forces are less likely to deal with mass scale unrest. They are increasingly used in raids on private homes, she said. Obama, on the other hand, is seeking to limit the use of military equipment to control citizen protests.

Ferguson Riots
Riot police stand guard as demonstrators protest the shooting death of teenager Michael Brown in Ferguson, Missouri, on August 13, 2014. Reuters/Mario Anzuoni

The plan announced by the White House on Monday acts on the recommendations of federal interagency working group led by the Departments of Justice, Defense and Homeland Security. The list of banned weapons includes tracked armored vehicles, weaponized aircraft and vehicles, bayonets, grenade launchers and large-caliber firearms, according to a report of the working group released Monday.

For other types of equipment, such as MRAP (mine-resistant ambush protected) vehicles and riot shields, departments will have to provide added justification for their use, according to a fact sheet released by the White House. Obama was expected to announce these steps during a visit later on Monday to Camden, New Jersey. He also plans to encourage trust-building between police and the communities that they serve.

A California National Guardsman stands watch over a riot-torn area of South-Central Los Angeles April 30, 1992 on the second day of rioting after a jury acquitted four Los Angeles police officers in the videotaped beating of motorist Rodney King. Reuters/Lou Dematteis