Troops from the National Guard were stationed throughout Congress on Wednesday, as its lower chamber prepared to make Donald Trump the first US president to be impeached not once, but twice.

They guarded the perimeter of the US Capitol and patrolled lawmakers’ offices. Inside the seat of America’s legislature, where troops were deployed as they had been during the Civil War, some were so exhausted that they lay down to nap, in full military gear, masked, and with guns by their sides.

Their presence epitomised a city, a country and a democracy teetering on the edge as it tried to complete the transfer of power between two US administrations.

The normally peaceful transition has been marred this time by Mr Trump’s repeated refusal to accept his election defeat to Joe Biden for weeks, and his incitement of the deadly January 6 attack on Congress by a group of supporters seeking to overturn the result.

“There are more troops right now in Washington DC than in Afghanistan,” said Seth Moulton, a Democratic lawmaker from Massachusetts. “And they are here to defend us against the commander-in-chief — the President of the United States — and his mob.”

Dressed in funereal black, Nancy Pelosi, the Democratic speaker of the House of Representatives, launched the impeachment proceedings on the floor of the lower chamber of Congress on Wednesday, just one week after the attack on the Capitol.

Her haste reflected a chilling determination by many Democrats — and even some Republicans — that after the most tumultuous, disruptive and erratic US presidency in recent memory, Mr Trump is unfit to serve in the White House for even a week longer.

“He must go,” Ms Pelosi said of the president during the impeachment debate on the House floor. “He is a clear and present danger to the nation that we all love.”

In the end, 10 House Republicans joined the Democrats seeking to remove Mr Trump, and the vote was not particularly close.

Among the defectors from the president’s party was Adam Kinzinger of Illinois. “It was a sobering moment to vote in support of impeachment today; to walk over to the US Capitol, our symbol of democracy, and recall the violent insurrection we witnessed here just one week ago,” he wrote on Twitter. “This is not a vote I took lightly, but a vote I took confidently. I’m at peace.”

The Democratic push for a second impeachment of Mr Trump gathered steam rapidly in recent days as lawmakers grew angrier at the assault on the Capitol and more details emerged of the threat to their own safety.

“Many members of the House were nearly assassinated,” Alexandria Ocasio-Cortez, the New York lawmaker, said on Instagram live on Tuesday night. “I had a very close encounter where I thought I was going to die.”

To add insult to injury, many Democrats were forced to huddle in enclosed spaces with maskless Republicans during the riot. Three Democratic lawmakers have since tested positive for coronavirus and Ms Pelosi announced she would introduce fines to force members of Congress to wear face coverings.

The Republican party, meanwhile, has become consumed by a gut-wrenching psychodrama over the fallout from the conduct of the president they had cheered and tolerated for so long.

Liz Cheney, the self-described “rodeo mom” and “constitutional conservative” who represents Wyoming in the House, led the charge to impeach Mr Trump. Jim Jordan of Ohio, one of the president’s most steadfast allies and defenders, responded by saying she should be removed from the party leadership.

The fissures in the Grand Old Party were everywhere. Nancy Mace, a first-term Republican member of Congress from South Carolina, became embroiled in a heated text message exchange with Marjorie Taylor Greene, another newly elected gun-toting lawmaker from Georgia who has been sympathetic to QAnon.

“I’m disgusted by what you and other Q-conspiracy theorists did last week in the chamber after all of the violence,” Ms Mace wrote, according to Axios. Ms Greene retorted that she should not believe the “fake news”.

Lauren Boebert, the gun-toting first-term Republican from Colorado and a defender of the president, set off a metal detector as she came into work this week and protested the new security measure imposed by Ms Pelosi.

“Metal detectors outside of the House would not have stopped the violence we saw last week — it’s just another political stunt by Speaker Pelosi,” Ms Boebert said.

US House votes to impeach Donald Trump for a second time

In the Senate, Mr Trump’s actions put Mitch McConnell, the unflappable 78-year-old Republican leader, in the most difficult position of his political career. The New York Times reported that Mr McConnell believed that the president had committed “impeachable offences” and was privately pleased with the House proceedings, but the backlash from his fellow lawmakers was swift.

Lindsey Graham, the South Carolina senator, said Republican leadership entertaining a swift conviction were making the problem “worse, not better” and impeachment was “the last thing the country needs”. Mr McConnell later said he would not move swiftly to try Mr Trump in the Senate but noted that he was still undecided on whether to convict the president.

Concerns of extremist attacks at Mr Biden’s inauguration next week have been rising, forcing Washington DC’s authorities to discourage travellers to the city, Airbnb to cancel reservations in the capital, and the president-elect to scrap his plan to travel to his swearing-in by train from Delaware.

Banned by Twitter, his favourite means of communication, Mr Trump made two interventions on Wednesday, the first of which was a statement from the White House appealing for “NO violence, NO lawbreaking and NO vandalism”.

In a sign of growing alarm among law enforcement officials over the threat of further violence, Mr Trump followed up with an uncharacteristic video message in which he urged supporters of “our agenda to be thinking of ways to ease tensions, calm temperatures and help to promote peace in our country”.

Mr Trump’s video made no mention of his impeachment, his election loss, Mr Biden, or the peaceful transfer power. The last time he addressed any of that was on Tuesday, during a trip to Alamo, Texas, where he touted his unfinished wall along the US-Mexico border.

“Be careful what you wish for,” he said, in a thinly-veiled threat to those voting to charge him. “The impeachment hoax is a continuation of the greatest and most vicious witch hunt in the history of our country and is causing tremendous anger and division and pain.”

It was, Mr Trump added, “very dangerous for the USA, especially at this very tender time”.