President Joe Biden made up his mind about Afghanistan months — really years — ago.

For more than a decade, Biden advocated for an end to American involvement in Afghanistan. But he did so as something of an outsider, a senator whose ultimate power came in the form of a single vote on Capitol Hill or a vice president who advised another president.

But authority over America's longest war finally fell into Biden's hands this year and he insisted that the US withdraw from Afghanistan, settling on an August 31 deadline. And despite the rapid collapse of the Afghan government, spurring a humanitarian crisis and searing criticism at home and from traditional allies, he was resolute, at times defiant. He took responsibility and in turns leveled blame at his predecessor.

After months of largely focusing on quelling the pandemic and stimulating the economy, the chaos in Afghanistan triggered the first foreign policy crisis of Biden's presidency, temporarily drowning out his other priorities. His response offers a fuller picture of how Biden approaches his job, relying on a political sensibility he built as a veteran of the Senate who has weathered decades of Washington tumult and scandal.

How Biden is handling the weight of his decision to end the war is a product of his 40 years in public life, many of them spent studying the world. He sold voters on his experience and this is the first time he is offering decisions, not mere opinions in a Senate hearing — and he will be judged by the outcome, which is far from clear at this point. Americans are seeing a different side of Biden during this crisis, a sterner, sometimes testy man known much better for his empathy.

In the face of setbacks that would prompt most politicians to step back and offer some level of contrition, Biden has only grown firmer in his position this week.

He has acknowledged that the Taliban advanced faster than expected but has said, both privately to aides and in a pair of public addresses to the American people, that the swift collapse of the Afghan government proved correct his longstanding skepticism of the war effort.

“If anything, the developments of the past week reinforced that ending US military involvement in Afghanistan now was the right decision,” he said Monday, as he sought to sidestep blame for the disorderly withdrawal.

Biden’s view on American military power

Biden's decision laid bare a cold realism in his view of American military power: American forces shouldn't be used to promote the nation's ideals abroad.

Troops, in Biden's estimation, should be focused more narrowly on threats to the homeland, and the nation's diplomatic and economic might are the proper tools to uphold its values overseas.

It's a sentiment the White House believes Americans agree with after nearly two decades of endless conflicts, but one that comes with painful cost for tens of thousands of Afghans who assisted the US occupation or thrived under it.

To advisers, he's reiterated that his opposition to the 2009 surge in Afghanistan ordered by President Barack Obama was one of his proudest moments in government.

That confidence, which even some allies say sometimes borders on obstinance, has been a defining force in Biden's political life and now his presidency. When he believes he is in the right, current and former aides say, there is little talking him out of it.

His commitment to causes has been evident throughout his career, according to his former Senate colleague Trent Lott, underscored even by the length of his speeches.

“He was prone to making long speeches on the Senate and I used to joke, We can go get something to eat, this is going to be a while,' but they were good speeches and it's what he believed in,” Lott, a Mississippi Republican, said.

That sense of clarity, sometimes bordering on rigidity, helped Biden overcome a childhood stutter and sustained his sagging third presidential campaign through the doldrums of 2019 to an upset nomination a year ago. In the White House, it was his own zeal to reach a bipartisan infrastructure accord that propelled the legislation through the divided Senate earlier this month.

It was on display again Friday as Biden insisted, despite a mounting chorus of condemnation from allies abroad, that the haphazard American withdrawal from Afghanistan was improving the country's stature overseas.

“The fact of the matter is I have not seen that,” Biden maintained when asked about allies from the United Kingdom to Germany that have publicly questioned America's credibility. “Matter of fact, the exact opposite. I've got the exact opposite thing as we're acting with dispatch, we're acting, committing to what we said we would do.” Biden acknowledged for the first time at length the heart-wrenching scenes of confusion as Americans, allies and Afghans struggle to flee the Taliban. But he was adamant that his decision was the right one, saying he always envisioned some amount of chaos in the pullout.

“There's no way in which you'd be able to leave Afghanistan without there being some of what you're seeing now,” Biden said.

Despite Biden's confidence, the administration's initial public response was faltering.

The president was at Camp David as part of his summer vacation but scrambled back to the White House on Monday, the day after Kabul fell. In his first public remarks on the situation, he admitted no fault for the chaotic drawdown.