Oath Keepers founder Stewart Rhodes began planning to resist the result of the 2020 US presidential election days after the vote, telling followers that Donald Trump “will need us and our rifles,” an FBI witness testified on Tuesday.

Rhodes and four co-defendants – Thomas Caldwell, Kenneth Harrelson, Kelly Meggs and Jessica Watkins – are on trial in federal court in Washington, accused of conspiring to prevent Congress from certifying the election victory of President Joe Biden in a failed bid to keep Trump, a Republican, in power.

On Tuesday, the second day of the trial, FBI Special Agent Michael Palian read to the court messages that he said Rhodes sent to his followers on 7 November 2020, around the time media outlets were calling the race for Biden, in which Rhodes warned that “the coup isn’t over” and that Biden’s fellow Democrats would also “steal” a majority in the Senate.

“Think of all our Founding Fathers did to defy and resist the abuses of King George and Parliament,” Palian, the government’s first witness, cited Rhodes as saying in an encrypted Signal message that referenced the leaders of the American Revolution who overthrew British colonial rule.

“Trump has one last chance, right now, to stand. But he will need us and our rifles,” Rhodes said, according to Palian’s testimony.

In their opening statement on Monday, prosecutors told a jury that Rhodes and the other defendants had plotted to do whatever it took to prevent the transfer of presidential power.

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Defense attorneys said the Oath Keepers were a peace-keeping group and vowed the evidence would show that the defendants had done nothing illegal.

Palian, testifying for a second day, said Rhodes had organized an Oath Keepers conference call on 9 November 2020, during which he told members their mission was to go to Washington.

“We’re very much in exactly the same spot that the Founding Fathers were in like March 1775,” Rhodes said on the call.

Rhodes said on the call that Trump should invoke the Insurrection Act, Palian testified. The Insurrection Act is a law that empowers the president to deploy the military to suppress civil disorder.

“And to get him to do that, he has to know that the people are behind him, and that he will not be deserted,” Rhodes said on the call. “So we’ve gotta be in DC.”

Trump supporters stormed the Capitol after the former president falsely claimed the election had been stolen from him through widespread fraud. Five people died during or shortly after the riot, and about 140 police were injured.

The five on trial face numerous felony charges, including seditious conspiracy – a Civil War-era statute that is rarely prosecuted and carries a statutory maximum sentence of 20 years in prison.

Prosecutors have said the defendants trained and planned for 6 January, stockpiling weapons at a northern Virginia hotel outside the capital for a so-called “quick reaction force” that would be ready if called upon to transport arms into Washington.

As lawmakers met to certify Biden’s election victory, some Oath Keepers charged into the Capitol building, clad in paramilitary gear.

The government and extremist monitoring groups have characterized the Oath Keepers as a far-right anti-government group, some of whose members have ties to militias. Some of the members include current and former military and law enforcement personnel.

Rhodes, a Yale-educated attorney and former US Army paratrooper, has disputed that characterisation.