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

The FBI, DHS, Secret Service and U.S. Capitol Police, along with several local law enforcement agencies, have issued an extensive "threat assessment" surrounding Wednesday's inauguration.

It covers a range of threats surrounding the inauguration, including not only physical threats from domestic terrorists but also influence campaigns from Russia, China and Iran stemming from the Capitol siege. It even covers physical threats from drones.

The memo says domestic extremists is the “most likely” threat to the inauguration, citing recent incidents of ideologically motivated violence, including the deadly mob at the U.S. Capitol building.

Regarding foreign concerns, the assessment said that since the incident at the Capitol, “Russian, Iranian, and Chinese influence actors have seized the opportunity to amplify narratives in furtherance of their policy interest amid the presidential transition.”

“We have not identified any specific, credible information indicating that these actors intend to explicitly commit violence,” it added. “Furthermore, we have not identified any specific, credible cyber threat to critical infrastructure supporting the upcoming Presidential Inauguration nor a specific credible cyber threat to military or law enforcement personnel supporting the event."

The memo did say, however, that Russian state media has “amplified themes related to the violent and chaotic nature of the Capitol Hill incident, impeachment of President Trump, and social media censorship.”

Iranian state media has “continued to stoke claims that President Trump encouraged and incited the violence, as well as calls to invoke the 25th amendment,” the memo added. It has also “amplified perceived concerns related to President Trump’s mental health and the prospect of other risky actions he could take before leaving office.”

Finally, it noted that Chinese media has “seized the story to denigrate US democratic governance -- casting the United States as broadly in decline -- and to justify China’s crackdown on protestors in Hong Kong."

Lastly, the memo warned that drones could disrupt law enforcement operations at the inauguration, though it added that it does not have “specific, credible information” indicating malicious actors have plans to use unmanned aircraft systems to target the event.

-ABC News’ Mike Levine