WASHINGTON — Rioters locked up for their roles in the Jan. 6 Capitol attack were released while judges began dismissing dozens of pending cases Tuesday after President Donald Trump’s sweeping grant of clemency to all 1,500-plus people charged in the insurrection that shook the foundation of American democracy.

With the stroke of a pen on his first day back in the White House, Trump’s order upended the largest prosecution in Justice Department history, freeing from prison people caught on camera viciously attacking police as well as leaders of far-right extremist groups convicted of orchestrating violent plots to stop the peaceful transfer of power after his 2020 election loss.

More than 200 people convicted of Jan. 6 crimes were released from federal Bureau of Prisons custody by Tuesday morning, officials told The Associated Press.

The pardons and commutations cement Trump’s efforts to downplay the violence that left more than 100 police officers injured as the mob fueled by his lies about the 2020 election stormed the Capitol and halted the certification of President Joe Biden’s victory.

Trump’s decision to grant clemency to even rioters who assaulted police — whom his own vice president recently said “obviously” shouldn’t be pardoned — underscores how Trump has returned to power emboldened to take actions once believed politically unthinkable. And it shows how Trump plans to radically overhaul the Justice Department that also brought criminal charges against him in two cases he contends were politically motivated.

“The implications are clear,” said Julian Zelizer, a Princeton University historian. “Trump will go to great lengths to protect those who act in his name. This is the culmination of his effort to rewrite Jan 6, in this case using his presidential muscle to free those who were part of a violent assault on the Capitol.”

As defendants celebrated their release outside lockups across the country, the federal prosecutor’s office in Washington that spent the last four years charging rioters filed a flurry of motions to dismiss cases that have yet to go to trial. The motions were marked with the name of the man Trump has named to lead, at least temporarily, the capital’s U.S. attorney’s office — Ed Martin, a board member of a group called the Patriot Freedom Project, which portrays the Jan. 6 defendants as victims of political persecution.

The former leaders of the Oath Keepers and Proud Boys, who were convicted of seditious conspiracy in the most serious charges brought by the Justice Department, were both released from prison hours after Trump signed the clemency order. Stewart Rhodes, of Granbury, Texas, was serving an 18-year prison sentence, and Enrique Tarrio, of Miami, was serving a 22-year sentence.

About 100 people gathered in frigid temperatures outside the District of Columbia jail, where a handful of Jan. 6 defendants remained behind bars as of Tuesday morning.

Among those in the crowd was Robert Morss, a former Army Ranger and high school history teacher who was sentenced to more than five years in prison for his attacks on police at the Capitol. Morss was released late Monday from a halfway house in Pittsburgh and drove through the night to support defendants jailed in Washington.

Another Jan. 6 defendant, Kevin Loftus, traveled to the jail in Washington after his release from another lockup. Loftus was sentenced in December to six months behind bars for violating the terms of his probation after trying to fly overseas to join the Russian military and fight against Ukraine. He said he was going to have the pardon from Trump framed.