Mr Biden hired Jake Sullivan, his national security advisor, to conduct an inter-agency inquiry into Afghanistan policy, which resulted in 10 departmental meetings, three cabinet-level meetings, and four meetings in the camp room attended by the president.

The Biden team considered other options, including maintaining a small troop presence for counter-terrorism operations or in support of the Afghan security forces, but argued that this was just “magical thinking” and would require more troops than was bearable. They debated whether to renegotiate the Trump deal to make further concessions, but the Taliban made it clear they would not return to the negotiating table and considered the Trump deal binding.

Mr Biden’s advisors also considered extending the withdrawal period until winter, after the traditional fighting season was over, to make the transition less dangerous for the Afghan government. The Afghanistan Study Group, a bipartisan, Congressional chartered body led by General Joseph F. Dunford Jr., a retired chairman of the Joint Chiefs, and which included Ms. O’Sullivan, recommended the deadline for the February May 1st extend out and seek better conditions.

But Mr Biden was warned by security experts that the longer it took for a decision to be announced, the aides said, the more dangerous it would get, so he only extended it until August 31.

Particularly influential on Mr Biden, aides said, were a series of intelligence assessments he had requested of Afghanistan’s neighbors and close neighbors, which revealed that Russia and China wanted the United States to remain stuck in Afghanistan.

At the end of the day, officials said that either option eventually led to one of the two ultimate alternatives – wholly out, as Mr. Trump had agreed, or preparing for a longer and more dangerous gun war with many other troops. Although not everyone in the room preferred Mr. Biden’s path, officials claimed everyone was heard.

“Biden faced basically the same problem as Trump,” said Vali Nasr, a senior adviser to Richard C. Holbrooke, Obama’s special envoy on Afghanistan and Pakistan, “and his answer was the same – we’re not going.” To get back in, you have to we out. “