Oath Keepers founder Stewart Rhodes was sentenced to 18 years in prison on Thursday for his role in the Jan. 6, 2021 attack on the U.S. Capitol.
It marks the first sentence for seditious conspiracy in relation to the deadly insurrection after a landmark verdict last year convicted Rhodes of plotting to keep former President Donald Trump in power.
Rhodes was convicted of the rarely-used seditious conspiracy charge in November, alongside Kelly Meggs, another leader of the far-right group. Four others were convicted of the same during a second trial in January.
During Thursday's sentencing, prosecutors made a case for terrorism enhancement for Rhodes' sentence, saying he was someone "who for weeks if not months orchestrated and then led this conspiracy, who repeatedly advocated for the use of force."
Meggs is expected to be sentenced later Thursday, with the other Oath Keepers due to be sentenced on Friday and next week.
Rhodes, 57, is a former U.S. Army paratrooper who studied law at Yale University.
Rhodes' sentencing comes weeks after the leader of another far-right group, the Proud Boys, was convicted on the same charge for a separate plot to block the transfer of presidential power.
The members of the Proud Boys will face sentencing in August and September.
More than 950 people have been arrested in nearly all 50 U.S. states for participating in the unprecedented riots that left five people dead.