Mr. Biden assigned Jake Sullivan, his national security adviser, to run an interagency examination of Afghanistan policy that resulted in 10 meetings of department deputies, three cabinet-level meetings and four meetings in the Situation Room that included the president.

The Biden team considered other options, including keeping a small presence of troops for counterterrorism operations or to support Afghan security forces but reasoned that was just “magical thinking” and would take more troops than was sustainable. They discussed whether to renegotiate the Trump agreement to extract more concessions but the Taliban made clear it would not return to the bargaining table and considered the Trump deal binding.

Mr. Biden’s advisers also considered extending the withdrawal deadline until the winter, after the traditional fighting season was over, to make the transition less dangerous for the Afghan government. The Afghanistan Study Group, a bipartisan congressionally chartered panel that was led by Gen. Joseph F. Dunford Jr., a retired Joint Chiefs chairman and that included Ms. O’Sullivan, in February recommended extending the May 1 deadline and seeking better conditions before pulling out.

But Mr. Biden was warned by security specialists that the longer it took to withdraw after a decision was announced, the more dangerous it would become, aides said, so he extended it only until Aug. 31.

Particularly influential on Mr. Biden, aides said, were a series of intelligence assessments he requested about Afghanistan’s neighbors and near neighbors, which found that Russia and China wanted the United States to remain bogged down in Afghanistan.

At the end of the day, then, the officials said every option eventually led to one of the two ultimate alternatives — get out altogether, as Mr. Trump had agreed to do, or prepare for a prolonged and more dangerous shooting war with many more troops. While not everyone in the room preferred Mr. Biden’s path, officials maintained that everyone was heard.

“Biden basically faced the same issue that Trump faced,” said Vali Nasr, who was a senior adviser to Richard C. Holbrooke, Mr. Obama’s special representative on Afghanistan and Pakistan, “and his answer was the same — we’re not going to go back in, we have to get out.”