WASHINGTON • The leader of the right-wing Oath Keepers group was ordered to serve 18 years in prison for his role in the 2021 attack on the U.S. Capitol and conspiring to use force to keep Donald Trump in power after he lost the 2020 presidential election.

Stewart Rhodes, 58, was sentenced Thursday in Washington by U.S. District Judge Amit Mehta, who ruled the actions of the group leader amounted to terrorism. Rhodes is one of 10 defendants convicted at trial of seditious conspiracy — four more pleaded guilty to that crime — for their actions on Jan. 6, 2021. Among them were other Oath Keepers and leaders of the farright Proud Boys who have yet to be sentenced.

The prison term imposed by Mehta was the longest handed down in the government’s prosecution of more than 1,000 people over the storming of the Capitol, which disrupted the certification of the election of Joe

Biden as president.

The riot involved assaults on 140 police officers and caused more than $2 million in property damage.

“Seditious conspiracy is among the most serious crimes an individual American can commit,” Mehta said. The attack on the Capitol was “one of the blackest days in the history of our country.”