Stewart Rhodes, the founder and leader of the right-wing Oath Keepers militia, has been arrested and charged with seditious conspiracy in connection with the Jan. 6 riot at the U.S. Capitol, according to court documents released Thursday.

This marks the first time defendants related to the deadly Jan. 6 insurrection have been charged with seditious conspiracy. Rhodes and Edward Vallejo of Phoenix, Arizona, were arrested Thursday; the remaining defendants were already facing charges related to the Capitol attack.

The indictment accuses Rhodes and the other members of the extremist group with conspiring "to oppose the lawful transfer of presidential power by force, by preventing, hindering, or delaying by force execution of laws governing the transfer of power."

Authorities said members of the extremist group came to Washington with the intent of stopping the certification of President Joe Biden’s victory in the 2020 election.

"The seditious conspiracy indictment alleges that, following the Nov. 3, 2020, presidential election, Rhodes conspired with his co-defendants and others to oppose by force the execution of the laws governing the transfer of presidential power by Jan. 20, 2021," the Justice Department wrote in a statement. "Beginning in late December 2020, via encrypted and private communications applications, Rhodes and various co-conspirators coordinated and planned to travel to Washington, D.C., on or around Jan. 6, 2021, the date of the certification of the electoral college vote, the indictment alleges. Rhodes and several co-conspirators made plans to bring weapons to the area to support the operation. The co-conspirators then traveled across the country to the Washington, D.C., metropolitan area in early January 2021."

According to the indictment, the defendants conspired by organizing into teams "that were prepared and willing to use force and to transport firearms and ammunition into Washington, D.C.," recruiting members and affiliates, organizing trainings for "paramilitary combat tactics," bringing weapons and supplies including knives, batons, helmets, tactical vests and radio equipment to the Capitol, breaching and attempting to take control of the Capitol on Jan. 6, attacking law enforcement inside the Capitol and continuing to plot after Jan. 6 "to oppose by force the lawful transfer of presidential power, and using websites, social media, text messaging and encrypted messaging applications to communicate with co-conspirators and others."

Seditious conspiracy is defined under U.S. Code as: "If two or more persons in any State or Territory, or in any place subject to the jurisdiction of the United States, conspire to overthrow, put down, or to destroy by force the Government of the United States, or to levy war against them, or to oppose by force the authority thereof, or by force to prevent, hinder, or delay the execution of any law of the United States, or by force to seize, take, or possess any property of the United States contrary to the authority thereof, they shall each be fined under this title or imprisoned not more than twenty years, or both."

Rhodes, an Army veteran who founded the Oath Keepers in 2009 as a reaction to the presidency or Barack Obama, had been saying for weeks before the Jan. 6, 2021 Capitol riot that his group was preparing for a civil war and was "armed, prepared to go in if the president calls us up."

The 56-year-old is now the highest-ranking member of an extremist group to be arrested in relation to the attack, where a mob of supporters of former President Donald Trump stormed the Capitol in an attempt to overturn the results of the 2020 presidential election. Rioters stormed past police barriers and smashed windows, injuring dozens of officers and sending lawmakers fleeing for their lives.

Rhodes did not enter the Capitol building on Jan. 6 but is accused of helping put into motion the violence that disrupted the certification of the vote. The Oath Keepers case is the largest conspiracy case federal authorities have brought so far over Jan. 6.

The indictment against Rhodes alleges Oath Keepers formed two teams, or “stacks,” that entered the Capitol. The first “stack” split up inside the building to separately go after the House and Senate. The second “stack” confronted officers inside the Capitol Rotunda, the indictment said.

Outside Washington, the indictment alleges, the Oath Keepers had stationed two “quick reaction forces” that had guns “in support of their plot to stop the lawful transfer of power.”

Rhodes' attorney Jonathan Moseley confirmed the arrest and said that the militia leader "has been subject to a lot of suspicion to why he wasn’t indicted" in relation to the Jan. 6 riot.

"I don’t know if this is in response to those discussions, but we do think it’s unfortunate," Moseley said. It’s an unusual situation."

In a speech last week, Attorney General Merrick Garland pledged to hold those responsible for the Jan. 6 attack to account, regardless of "whether they were present that day or were otherwise criminally responsible for the assault on democracy."

“Those involved must be held accountable," Garland said. "And there is no higher priority for us at the Department of Justice.”

"We will follow the facts wherever they lead," he added. "The actions we have taken thus far will not be our last."

The Associated Press contributed to this report.