Nearly a year and a half ago, a mob of about 2,000 supporters of former President Donald Trump stormed the U.S. Capitol in a destructive rampage, trying to block lawmakers from certifying Democrat Joe Biden’s decisive victory in the 2020 presidential election.

Starting Thursday night, Americans will get a first-hand accounting of how the attack on January 6, 2021, unfolded. Witnesses will testify before a congressional investigative committee about the planning of the insurrection, Trump’s role in promoting the mayhem, how he tried to thwart election results to claim another four-year term, and what he was doing at the White House during the rampage that was televised across the globe.

FILE - Insurrections loyal to President Donald Trump riot outside the Capitol, Jan. 6, 2021, in Washington.

FILE – Insurrections loyal to President Donald Trump riot outside the Capitol, Jan. 6, 2021, in Washington.

It was a seminal moment in America, an attack on the seat of American democracy. The Capitol is often seen around the world as the symbol of a freely elected representative form of government and the place where the power of the presidency is peacefully passed from one president to the next.

In the first of at least six days of hearings this month, some of them televised in prime time, witnesses are expected to tell the U.S. House select committee investigating the January 6 attack how Trump acolytes supported the insurrection in a futile attempt to keep him in power.

The committee is planning a combination of live testimony from key Trump administration insiders; videotaped interviews with others, including Trump’s daughter Ivanka and her husband, Jared Kushner — both of whom were White House advisers — and previously undisclosed video of the hours of chaos inside the Capitol building.

Committee investigators have interviewed more than 1,000 witnesses linked to the riot and Trump’s effort to upend the election results. Among them is Cassidy Hutchinson, a top assistant to former White House chief of staff Mark Meadows, who reconstructed details of White House meetings and discussions for the committee.

But other possible witnesses, including Meadows, other key Trump aides and five Republican congressmen with links to Trump have all refused to testify. Short of a late-minute change of mind, they are likely to succeed in stonewalling the committee’s efforts to have them appear. Meadows initially provided House investigators with voluminous records before refusing to testify.

Two former Trump advisers, Peter Navarro and Steve Bannon, have been charged with contempt of Congress for refusing to testify before the committee, but the Justice Department decided to not bring contempt charges against Meadows and another former Trump aide, Dan Scavino, who also refused to testify.

To this day, Trump claims he was cheated out of re-election by fraudulent vote counts in several closely contested states, although recount after recount showed minimal irregularities — not enough to upend the national outcome. Trump has lost five dozen court suits contesting the vote. He has derided the congressional investigation.

The nine-member committee — seven Democrats and two Republicans who turned against the former president — is expected to call witnesses to describe Trump’s efforts to persuade then-Vice President Mike Pence to overturn the national results, which would have thrown the outcome of the election into legal chaos.

But Pence refused Trump’s overtures, saying his role as presiding officer over certification of the votes from all 50 states was merely administrative and that he had no power to overturn the official count.

As it turned out, the unofficial results ahead of the official certification proved to be the same as when the state counts were tallied in the early hours of January 7, 2021: a 306-232 Biden victory in the Electoral College.

U.S. presidents are chosen by the Electoral College, a system of counting states’ electoral votes based on the popular vote outcome in each state. The number of electoral votes is based on a state’s population and its total number of senators and representatives in Congress.

As the hearings start, one of the Republicans on the committee, Representative Liz Cheney, told CBS News on Sunday, “People must pay attention. People must watch, and they must understand how easily our democratic system can unravel if we don’t defend it.”

‘Fight like hell’

Just ahead of the official certification of his electoral loss, Trump staged a rally near the White House, telling thousands of supporters to head to the Capitol to “stop the steal” and “fight like hell” to block certification of Biden’s win.

About 2,000 of his supporters stormed into the U.S. Capitol, smashing windows and doors, ransacking offices and scuffling with police, injuring 140 of them. Five people died that day or in the immediate aftermath. One protester was fatally shot by a Capitol Police officer during the riot.

To this point, at least 861 people have been charged with criminal offenses committed at the Capitol. Many have faced minor trespassing charges, while others have been charged with assaulting police, damaging parts of the Capitol and ransacking congressional offices.

At least 306 of those arrested have pleaded guilty, with many sentenced to a few weeks in jail. Some who faced assault charges have been sentenced to more than four years. The rest of the cases remain unresolved as investigators pore through vast video footage of the mayhem to identify the rioters.

Trump says he supports those charged in the attack on the Capitol and has said if he runs for the presidency in 2024 and wins, “we will treat those people from January 6 fairly. And if it requires pardons, we will give them pardons, because they are being treated so unfairly.”