January 6th Capitol riot: Who are the Oath Keepers and why are they on trial?

Members of the Oath Keepers, a far-right militia group, are on trial in one of the most high-profile cases stemming from the 6 January 2021 attack on the US Capitol.

The group's leader, Stewart Rhodes, is charged, along with four others, with seditious conspiracy - plotting to oppose the transfer of presidential power. All have pleaded not guilty.

Here's what you need to know about the case.

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".

Prosecutors say Mr Rhodes began a campaign to reject the results of the November 2020 presidential election two days after the vote, while ballots were still being counted.

On 5 November, the Oath Keepers' leader told supporters on Signal, a private messaging app: "We aren't getting through this without a civil war. Too late for that. Prepare your mind, body, spirit."

Mr Biden was declared the winner of the election on 7 November, following days of vote-counting.

According to a federal indictment, Mr Rhodes and others bought thousands of dollars of weapons and gear over the next two months, made plans to stash guns, and organised members into military-style units.

On 6 January 2021, a mix of groups - along with hundreds of individuals apparently unconnected to any organisation - assembled outside the Capitol after then-President Donald Trump held a rally nearby.

Those who gathered included Oath Keepers, members of the all-male far-right Proud Boys, militia groups such as the Three Percenters, and believers in QAnon, a conspiracy theory.

In the months since the violence, evidence has emerged of prior planning and potential co-ordination between groups. For instance, footage shot by documentary maker Nick Quested shows Mr Rhodes meeting Enrique Tarrio, leader of the Proud Boys, on the evening of 5 January 2021.

There's no evidence that Mr Rhodes himself entered the Capitol on the day of the attack, but prosecutors say that other members of Oath Keepers did.

In total, more than 870 people have been arrested in connection with the attack, according to Department of Justice figures.

The case against the Oath Keepers group is notable because it includes some of the most serious charges to date. Seditious conspiracy is a crime involving a plot to attack or overthrow the state, but which stops short of treason - waging war against the government.

Mr Rhodes and others are accused of continuing to plot after the riot. On the evening of 6 January he sent another message: "Patriots entering their own Capitol to send a message to the traitors is NOTHING compared to what's coming."

"This is certainly one of the biggest trials to date for the Department of Justice in their [6 January] prosecutions," said Jon Lewis, research fellow at George Washington University's Program on Extremism.

The trial could also show how the group has splintered since the Capitol riot. Three Oath Keepers have already pleaded guilty to seditious conspiracy and could be called as witnesses at the trial.

If convicted, the five could face up to 20 years in prison. On trial alongside Mr Rhodes are:

In total, at least 20 Oath Keepers members have been charged with a variety of crimes, and Mr Tarrio and other Proud Boys members will stand trial on seditious conspiracy charges in December.