WASHINGTON>> Oath Keepers extremist group founder Stewart Rhodes was sentenced Thursday to 18 years in prison for orchestrating a weeks-long plot that culminated in his followers attacking the U.S. Capitol in a bid to keep President Joe Biden out of the White House after he won the 2020 election.

Rhodes, 58, is the first person convicted of seditious conspiracy in the Jan. 6, 2021, attack to receive his punishment, and his sentence is the longest handed down so far in the hundreds of Capitol riot cases.

It’s another milestone for the Justice Department’s sprawling Jan. 6 investigation, which has led to seditious conspiracy convictions against the top leaders of two far-right extremist groups authorities say came to Washington prepared to fight to keep President Donald Trump in power at all costs.

“The Justice Department will continue to do everything in our power to hold accountable those criminally responsible for the January 6 attack on our democracy,” Attorney General Merrick Garland said in a statement.

In a first for a Jan. 6 case, the judge agreed with the Justice Department that Rhodes’ actions should be punished as “terrorism,” which increases the recommended sentence under federal guidelines. That decision could foreshadow lengthy sentences down the road for other far-right extremists, including former Proud Boys leader Enrique Tarrio, who also have been convicted of the rarely used charge.

Before announcing Rhodes’ sentence, U.S. District Judge Amit Mehta described a defiant Rhodes as a continued threat to the United States and democracy. The judge expressed fear that what happened Jan. 6 could be repeated, saying Americans will “now hold our collective breaths every time an election is approaching.”

“You are smart. You are charismatic and compelling, and frankly that’s what makes you dangerous,” the judge told Rhodes.

“The moment you are released, whenever that may be, you will be ready to take up arms against your government.”

Rhodes did not use his chance to address the judge to express remorse or appeal for leniency but instead claimed to be a “political prisoner,” criticized prosecutors and the Biden administration and tried to play down his actions on Jan. 6.

“I’m a political prisoner, and, like President Trump, my only crime is opposing those who are destroying our country,” said Rhodes, who appeared in Washington’s federal court wearing orange jail clothes.