What did Joe Biden know and when did he know it?

After the devastating debacle in Afghanistan, the president has to answer that question. He said in his televised speech that he wants to “be honest” with the American people, but so far, his explanations have left huge holes.

Did he receive profoundly flawed intelligence? Was he misled into believing that Afghan forces could hold off the Taliban long enough to ensure a safe and orderly departure of U.S. forces and allies?

Or was he told the truth: that the Afghan military, after a trillion dollars and years of training from Washington, was a fragile fraud that would collapse immediately without American support? And if he was told the truth, why did he choose to ignore the warning signs?

After Biden’s address, Leon Panetta, who served as Secretary of Defense under Barack Obama, told The Washington Post: “He didn’t really spend much time on the issue that I think really concerns the American people, which is the execution of that decision. What went wrong and how it is going to be fixed? It just struck me that they were crossing their fingers and hoping chaos would not result. And it doesn’t work that way.”

Biden made a totally rational and defensible decision that the Afghan mission was no longer “in our national security interest.” Moreover, he has the support of the American people. In a poll conducted last year by the National Opinion Research Center, only 22% called the Afghanistan effort a success.

But the botched execution of that decision was totally indefensible. It came just as the Biden administration is saying to the rest of the world: America is back. After years of dealing with a mercurial misfit in the White House, the new president represents a return to experience, competence and reliability.

Instead, the indelible images of chaos in Kabul sent a very different message. “It is a disaster in terms of American reputation,” Eliot A. Cohen, a military historian who teaches at Johns Hopkins, told the Post. “It’s a disaster in terms of our relationship with our allies. The sheer incompetence is terribly distressing.”

Moreover, added Cohen, the swift triumph of the Taliban is a “moral disaster,” because thousands of Afghan nationals who loyally served the American mission for many years have been left behind and now face mortal danger.

“Who’s going to trust us again?” Rep. Michael Waltz, a Florida Republican who served multiple tours in Afghanistan, told the Post. “Who’s going to trust us enough to risk not just their lives, but their entire family’s lives to stand with the United States, whether it’s protests in Cuba, whether it’s Taiwan? This is going to resonate for years.”

It’s difficult now to estimate the political price Biden could eventually pay, but if he runs again, images of the Afghan disaster will certainly be featured in GOP campaign ads against him.

So how did this happen? There’s strong evidence to indicate a massive intelligence failure. After all, barely a month ago, Biden said confidently, “The likelihood there’s going to be the Taliban overrunning everything and owning the whole country is highly unlikely.”

But there were also plenty of signs that Biden’s optimism was uninformed and ill-advised. “In fact,” reported the Post, “U.S. military officials privately harbored fundamental doubts for the duration of the war that the Afghan security forces could ever become competent or shed their dependency on U.S. money and firepower.”

If the military harbored those doubts, why wasn’t the president told? And if he was told, why didn’t he believe them?

Perhaps the answer lies in one of gravest mistakes any policymaker — or journalist, for that matter — can make: confirmation bias. It’s embracing evidence that reinforces your prejudices, while rejecting contradictory information. It’s the same sin, the Sin of Self-Delusion, that led to disaster in Vietnam.

“For 20 years, U.S. military leaders pretended the Afghan military they were supposed to be building was far more capable and cohesive than they knew it to be,” Georgetown law professor Rosa Brooks, a former Defense Department official under Obama, writes on Twitter. “And U.S. civilian leaders pretended to believe them, because it would have been too embarrassing for everyone to admit that we were screwing up and had neither the resources to fix things, nor the political will … It was not in anyone’s interest to be honest about Afghanistan.”

It’s now time for Biden to be honest. He owes that to our troops, to our allies, and to the American people.

Steven Roberts teaches politics and journalism at George Washington University. He can be contacted by email at stevecokie@gmail.com.