In the last decade, the US department of homeland security, established after the September 11 attacks, has handed out tens of billions of dollars in grants to local police.
Local law enforcement agencies have used that money to acquire battle gear designed for war rather than public safety.
"American law enforcement is and has always been paramilitary. We've simply seen an escalation, and a very large one, since 9/11 and leading into the Occupy movement as well …. They are a civilian police force but they operate according to a paramilitary organisational arrangement. It's a very heavily command-and-control oriented institution."
- Norm Stamper, a former Seattle police chief
An investigation by the Center for Investigative Reporting found that some police departments have been transformed into "army-like forces" because of the equipment they use.
Police say they need the combat gear to respond to terrorist attacks, such as the one in Mumbai in 2008, which included 11 coordinated shootings and bombings.
They say it is also needed to go up against well-armed criminals.
But the most visible use of that equipment has come as they dispersed largely peaceful protests like those seen at the height of the Occupy Wall Street movement.
In July this year, in the Californian city of Anaheim, police officers looked like they were prepared for war as they surrounded unarmed protesters demonstrating against police brutality.
So what are the risks of having militarised police forces in the US?
To discuss this with presenter Shihab Rattansi are guests: George Schulz, a co-author of the report by the Center for Investigative Reporting; Norm Stamper, a former Seattle police chief and author of Breaking Rank: A Top Cop's Expose of the Dark Side of American Policing; and Radley Balko, a senior writer at the Huffington Post.
"What we've been seeing in the last 10 years is even more disturbing .... The level of force that governments, politicians and law enforcement officials are choosing to use is not really based on a realistic assessment of the threat but increasingly based on what sort of political message that they want to send."
Radley Balko, a senior writer at the Huffington Post