A pro-gun, anti-government group launched in 2009, the Oath Keepers began with a rally in Lexington, Massachusetts - site of one of the first battles in the Revolutionary War.

Its founder, Mr Rhodes, is a former US Army paratrooper who studied at Yale Law School and was once an aide to libertarian Republican congressman Ron Paul of Texas.

The group is named after the oath of service that police, military and other officials take. Those taking the military oath, for instance, pledge to "support and defend the Constitution of the United States against all enemies, foreign and domestic".

The Oath Keepers focus recruitment on people with military and law enforcement experience, along with other frontline "first responders".

Extremism researchers have kept tabs on the group from the beginning, but it began to get a bigger profile when armed members started popping up in the middle of protests and civil unrest.

In 2014, they appeared at an armed standoff between a Nevada rancher and law enforcement. Later that year the Oath Keepers were spotted in Ferguson, Missouri, during protests after the shooting death of a black man, Michael Brown, by a police officer.