Biden followed through on his promise to swiftly end America's longest war and could be held responsible for the tragedy unfolding

• President Joe Biden decided to pull all troops out of Afghanistan back in April.
• He said "the Taliban overrunning everything and owning the whole country is highly unlikely."
• On Sunday, the Taliban took Kabul, and the US deployed 6,000 troops to secure the evacuation.

With the Taliban set to re-declare the Islamic Emirate of Afghanistan, President Joe Biden's decision to commit to a swift withdrawal has left the country and US personnel in peril.

Even though only about 2,500 troops were in Afghanistan when Biden announced the full withdrawal back in April, 6,000 are now being sent to secure the evacuation as conditions deteriorate amid the Taliban takeover.

"The likelihood there's going to be the Taliban overrunning everything and owning the whole country is highly unlikely," Biden said in July during a news conference, adding that Afghan troops were "as well equipped as any army in the world."

Biden said he was counting on the Afghan forces to be ready after nearly two decades of training from US soldiers, but without American air support and the myriad other capabilities the US can deploy as the world's preeminent military superpower, they've been rolled over by the Taliban.

The president also framed the withdrawal around a failure to establish democracy in Afghanistan, an aim that developed over the course of the Bush administration. What that focus leaves out is the broader purpose of American troop deployments across the globe.

In places like Germany or Japan - or even in nearby Kuwait where about 13,000 US troops are deployed - American military bases serve as strategic outposts.

They are not tasked with nation building but rather providing the US with influence and strike capabilities in a particular region if something horrible happens.

Biden's decision to put "trust" in the Afghan military by leaving them on their own led to the complete Taliban takeover he previously said was "highly unlikely."

Former Presidents Bush, Obama, and Trump all claimed the US was close to leaving Afghanistan and all made similar promises about the Afghans' ability to defend themselves, but the logistics of the withdrawal and the suffering that has ensued fall squarely on Biden.

While public opinion was initially behind the war at around 90% and eventually swung to wanting to leave the country by a majority of around 70%, the overarching shift in public opinion around the war does not indicate how little of a role it has played in American public life over the past two decades.

The compartmentalization of America's military presence is a complicated dynamic that precedes Biden and has much to do with how the public soured on the Vietnam War, but public opinion alone cannot explain the hasty and bungled troop withdrawal the president is overseeing.

A Brookings Institution analysis of polling on Afghanistan found "a significant degree of ambivalence" among Americans over whether to withdraw troops. They were generally more supportive of a more drawn-out timeline for removing US forces.

Biden chose to uphold the withdrawal agreement former President Donald Trump struck with the Taliban - whom Trump reportedly wanted to invite to Camp David - but he has broken with his predecessor on several other fronts, such as promising to return to the Iran nuclear deal and trying to reverse the "stay in Mexico" immigration policy. Biden campaigned on a pledge to end US military involvement in Afghanistan.

While the Biden administration is trying to depict the situation in Afghanistan as inevitable, the Taliban simply wasn't toppling provincial capitals when a couple thousand US troops were left on the ground for years.

Biden did stay true to his word, and he is following through on a campaign promise, but the withdrawal he ordered resulted in immediate violence and the swift fall of the Afghan government.