The first defendant to stand trial over the Capitol riots said that he would drag lawmakers "kicking and screaming" from the building, prosecutors say.
Guy Reffitt, 49, is accused of carrying a handgun on to the Capitol grounds, obstruction of an official proceeding and obstruction of justice among other charges.
Opening remarks for his criminal trial began on Wednesday.
The Texas man has pleaded not guilty to the five charges against him.
On 6 January, 2021, a mob of pro-Donald Trump rioters stormed the US Capitol as lawmakers gathered to certify Joe Biden's presidential election win. Prosecutor Jeffrey Nestler described it in opening remarks for Mr Reffitt's trial as "worst assault on the Capitol since the War of 1812", a date when British forces set fire to the White House.
He is accused of driving from Texas to Washington.
The prosecutor described Mr Reffitt as a "leader", saying he was "the tip of this mob's spear" that day.
He said that Mr Reffitt, who federal prosecutors accuse of being part of the Three Percenters militia group, had led rioters up the Capitol's stairs to storm the building.
The prosecutor said the Texas man, a drilling rig worker, had also texted a friend about plans to drag Democratic House of Representatives Speaker Nancy Pelosi and other lawmakers from the Capitol that day.
William Welch, the lawyer representing Mr Reffitt, gave a short opening statement, where he noted his client "does brag, he exaggerates and he rants" but that the "trial will be about fact versus hype". He also said Mr Reffitt had never entered the building.
More than 750 people have been arrested since the Capitol attack last year. Most have been charged with misdemeanours, but at least 40 have received prison sentences.
More than 200 people have pleaded guilty to various charges. Mr Reffitt, who was arrested on 19 January, 2021, is the first person facing criminal charges to stand trial. The trial is expected to be watched as a test case for future prosecutions.
Mr Reffitt's son and daughter are both expected to testify against him. According to a justice department affidavit, Mr Reffitt is accused of threatening his children if they turned him in to authorities for his alleged role in the Capitol riots.
Earlier this week, nine men and seven women were selected to serve on the jury, four as alternates.
Separately on Wednesday, Joshua James, a man with alleged ties to the far-right militia group the Oath Keepers, pleaded guilty in federal court as part of a plea agreement to a seditious conspiracy charge related to the Capitol riots.
A sedition charge is defined as attempting "to overthrow, put down or to destroy by force the government of the United States".
The leader of the Oath Keepers, Stewart Rhodes, and 11 others including James were charged in January with the crime over last year's attack.
The Department of Justice accuses Mr Rhodes of working with other Oath Keepers - a loosely knit militia that believes the US government has been corrupted by elites - to transport weapons and ammunition to Washington DC in their effort to block Mr Biden's presidency. Mr Rhodes has pleaded not guilty.