As procedural votes were underway in the House, Speaker Nancy Pelosi went outside the Capitol to thank the National Guard troops deployed to the complex in the wake of last week's riot and ahead of Biden's inauguration in one week.

Some National Guard members inside the Capitol were spotted taking in the sights of the Rotunda Wednesday morning, gathering around and listening to Rep. Brian Mast, R-Fla., an Army veteran who lost both legs in Afghanistan.

The Capitol has been closed to tours for months due to the coronavirus pandemic. With the exception of last Wednesday's attack, this is one of the few times visitors have snapped photos inside the building during the pandemic -- finding themselves with unique access as they've been designated to protect the building and lawmakers.

As lawmakers arrived on the Hill ahead of the House gaveling in to consider Trump's second impeachment, a heavy National Guard presence greeted them both outside and inside the building -- with some resting, embracing their rifles, on the floor of the Capitol.

Jane Campbell, the president and CEO of the United States Capitol Historical Society, confirmed to ABC News that troops have not been quartered in the Capitol since the Civil War -- when the Rotunda was still under construction, and the open-air space was used as a field hospital.

A Defense official said the National Guard members seen sleeping at the Capitol are on breaks and noted that it’s not uncommon on domestic or overseas deployments to see members taking breaks in between long shifts.

There are currently 6,600 members of the National Guard in Washington, D.C. with more continuing to flow in. A Defense official said Wednesday afternoon that the National Guard has now been authorized to have up to 20,000 Guardsmen in Washington for inauguration security and that most may be in town by this weekend.

-ABC News Luis Martinez and Benjamin Siegel

The first vote broke down along party lines 221-205, with Democrats voting to advance proceedings. Seven House members did not vote.

The House is now voting on the rule, which is expected to take roughly 45 minutes to one hour, the same amount of time. The chamber will then move to begin debate on the impeachment article.

-ABC News' Benjamin Siegel

As part of rule debate leading up to debate on the article of impeachment, Republicans have largely focused on procedural concerns, criticizing Democrats for moving quickly to impeach Trump without a full investigation and suggesting the move would further divide Americans.

"I hold him accountable for the attack on the Capitol," newly elected Rep. Nancy Mace, R-S.C., said, making her first speech on the House floor.

"If we're serious about healing the divisions in this country, Republicans and Democrats need to recognize that last week wasn't the first day of violence," she continued. "There is violence on both sides of the aisle."

"President Trump will leave office in seven days," Rep. Jason Smith, R-MO, said. "This is a reckless impeachment ... have a conscience."

Rep. Jim Jordan, R-Ohio, attacked Democrat Rep. Jim McGovern, the chairman of the House Rules Committee, over his 2017 objection to the election results, and accused Democrats of hypocrisy.

McGovern quickly shot back that Democrats and Hillary Clinton recognized Trump's victory -- when Republicans refused to acknowledge Biden's.

"The bottom line is this. This Capitol was stormed -- people died because of the big lies that were being told by this president and by too many other people on this side of the aisle. Enough!" McGovern said. "Coming up on this floor and talking about whataboutism and trying to make these false equivalences -- give me a break."

"The president of the United States instigated an attempted coup in this country," he added. "If this is not an impeachable offense I don't know what the hell is."

-ABC News' Benjamin Siegel

Several conservative House Republicans have criticized Rep. Liz Cheney since she announced she would support impeachment Tuesday evening.

The Wyoming Republican is the chair of the House GOP conference -- the No. 3 leadership position -- and was reelected to by GOP members at the start of this Congress.

"We ought to have a second vote," Rep. Jim Jordan, R-Ohio, told reporters Wednesday about the leadership position. "The conference ought to vote on that."

"She should not be serving this conference," Rep. Andy Biggs, R-Ariz., said Tuesday.

It's unclear how widespread the effort to remove Cheney from GOP leadership is. But Trump's top allies in the House are using impeachment as an opportunity to kneecap Cheney, a potential future speaker, after months of simmering tensions.

-ABC News' Benjamin Siegel

Barry Berke, the veteran New York defense lawyer who helped House Democrats argue President Donald Trump's first impeachment last year, will rejoin the House Judiciary Committee as the panel's lead impeachment lawyer for Trump's second trial, the panel announced Friday.

Berke will serve as chief impeachment counsel, supported by a team of attorneys from the House Judiciary and Oversight committees who helped Democrats make their case to the Senate last year that Trump abused his office by trying to pressure Ukraine's president to dig up dirt on then-candidate Joe Biden.

While House Speaker Nancy Pelosi, D-Calif., unveiled a team of nine new impeachment managers to make the case that Trump should be convicted of inciting the Capitol Hill riot that left five people dead, the presence of Berke and the rest of the legal team underscores the unique position House Democrats are in: For the first time in American history, they will have a team of lawyers behind them with experience arguing in a Senate impeachment trial.

Democrats could transmit the impeachment article to the Senate as early as next week, which could trigger the start of proceedings following Biden's inauguration on Wednesday.

There has been no official announcement on who will represent Trump in the trial, but personal lawyer Rudy Giuliani and Alan Dershowitz, who took part in the last trial, may be on the team, sources told ABC News. Trump favorite John Eastman, who led a failed election challenge to the Supreme Court, could also join the team.

-ABC News' Katherine Faulders and Benjamin Siegel