On Jan. 6 Americans witnessed on live television what few could have imagined: a violent, real-time invasion of the U.S. Capitol as part of an attempt to halt the peaceful transfer of power from one president to the next.

It has taken until now, seven months later, to even begin the congressional investigation that should have begun soon after these events. But that delay has not dimmed the power of the gut-twisting testimony offered Tuesday by four police officers who found themselves in hand-to-hand combat that day, determined to protect the Capitol and its inhabitants at the risk of their lives.

That it has taken so long to investigate is shameful testament to Republican leaders who are more worried about crossing former President Donald Trump than they are about defending our democracy. Of the 211 Republicans in Congress, only two — Rep. Liz Cheney of Wyoming and Rep. Adam Kinzinger of Illinois — had the courage and integrity to vote for the creation of the House Jan. 6 commission. Kinzinger, a former military officer, fought back tears listening to the officers' testimony, saying, "You guys may individually feel a little broken … but you guys won. You guys held."

He noted, correctly, that the reason not enough is known about that day is because "many in my party have treated this as just another partisan fight." He said this was "toxic and a disservice" to those who served at the Capitol, the American people and "the generations before us who went to war to defend self-governance."

If that sounds a bit grandiose, it's not after hearing testimony from officers. U.S. Capitol Police Sgt. Aquilino Gonell, an Army veteran who served in Iraq, said rioters called him a traitor and said, "If you shoot us, we all have weapons and we'll shoot back." Gonell was kicked, punched, sprayed. Rioters, he said, used hammers, police shields, rebar, knives, batons, bear spray and officers' own weapons against them. "It was like a medieval battle," he said.

Officer Daniel Hodges described lines of men fully outfitted in tactical gear who appeared to be coordinating efforts. At one point, there were nearly 10,000 rioters by some estimates, against 150 officers. This was no spontaneous demonstration that got out of hand, but a coordinated effort that took hours to push past barriers, viciously attack police and finally breach the Capitol itself.

Hodges heard rioters informing him, "You'll die on your knees." It was Hodges who was caught on a now infamous video clip, bleeding from the mouth and screaming while being crushed by the mob as he braced himself against a door, trying to prevent their entry.

Washington, D.C., Officer Michael Fanone went voluntarily to the Capitol because he "could not ignore what was happening." He was beaten unconscious, tased repeatedly at the base of his skull and suffered a heart attack, concussion and brain injury in the battle. At one point, he heard, "Kill him with his own gun," as rioters attempted to wrest his firearm from him. Still, Fanone said, "nothing has prepared me to address those elected members of government who deny the events of that day and in doing so betray their oath of office — those I was fighting so desperately to defend."

"It's disgraceful," he said, giving the table at which he was sitting a hard slap.

Capitol Officer Harry Dunn started his testimony asking a moment of silence for Officer Brian Sicknick, who died of a stroke the day after the battle. Dunn, who is Black, told of how he was repeatedly called the N-word, the first time that had ever happened while he wore a police uniform. He urged committee members to get to the bottom of the events of that day.

Cheney is right when she says that the investigation must know what happened every minute of that day in the White House, every phone call, every conversation, every meeting leading up to, during and after the attack. Tuesday's testimony, as powerful as it was, was only Step 1 in what must be a fearless and relentless look into what led up to the invasion of the Capitol. Officers testified that at a Black Lives Matter protest the previous summer, Capitol Police had ample resources and reinforcements in place from the start. What happened this time?

The committee will need access to phone records, texts and other documents. They should subpoena whoever they need testimony from, up to and including the former president and the current minority leader.

Dunn noted that Cheney and Kinzinger were being praised for their courage in stepping forward to be on the panel but questioned why. "Because they told the truth? Why is telling the truth hard? I guess in this America, it is," he said.

It shouldn't be.