WASHINGTON — The failure to rescue Afghanistan from the Taliban weighs on many American generals and diplomats. But few had as personal a stake as Zalmay Khalilzad.

Raised in Kabul and naturalized as a U.S. citizen, Mr. Khalilzad worked on Afghanistan policy under four American presidents before stepping down last month.

The battle for Afghanistan is lost, for now. But Mr. Khalilzad has embarked on a new fight: to defend his reputation against accusations that he bears special blame for the chaotic fall of Kabul, the Afghan capital, to the Taliban in August.

Mr. Khalilzad has been on a public-relations tour of sorts, sitting for numerous interviews in recent weeks to argue that he tried his best to broker peace despite vanishing leverage and an intransigent Afghan government. Calling his work incomplete, he is also applying unwelcome public pressure on the Biden administration to work with the Taliban.

His critics say the deal he reached with the Taliban under President Donald J. Trump was either delusional or cynical, a means of providing thin political cover for America’s abandonment of his native country.

Mr. Khalilzad “was the architect of the grand deception scheme,” Amrullah Saleh, who served as Afghanistan’s first vice president until the Taliban took control of Kabul, tweeted on Oct. 28. He said that Mr. Khalilzad treated Afghanistan “as a sacrificial goat,” caring for it “to the moment of slaughter.”

During a recent interview at his son’s high-rise apartment outside Washington, with sweeping views of the National Mall, Mr. Khalilzad rejected such criticism with a tone of bemused forbearance.

“I respect those who say, ‘This was a defining war for the future of the Islamic world, and no matter what we must prevail,’” he said. “Well, yeah. Sure, there’s a lot of things I wish for — but it wasn’t realistic, because they couldn’t convince the presidents, Congress and others.”

He added: “I tried to say, ‘OK, America wants to leave militarily. But let’s do also the right thing for Afghanistan. Because given my Afghan-ness, I was very much in touch with the feelings of the Afghan people. I took the job in part to see if I could end the war also for Afghanistan, for the people.”

The war ended on Mr. Khalilzad’s watch, but not on the terms he had hoped. Instead of the power-sharing government he imagined could restrain the Taliban, the militant group has assumed total control over the country, which is now facing economic collapse and famine.

“Zal emerges from this as a quite tragic figure,” said Eric S. Edelman, a former national security official who worked with Mr. Khalilzad under Presidents Ronald Reagan and George W. Bush.

As colleagues at the Pentagon in the late 1980s, Mr. Edelman and Mr. Khalilzad helped drive U.S. policy in support of mujahedeen fighters in Afghanistan resisting Soviet occupiers. During the Bush administration, they again backed resistance fighters, who this time were battling the Taliban as the United States invaded in 2001.

“He did a lot to create a modern, post-Taliban independent state,” Mr. Edelman said of Mr. Khalilzad. “And then to be in part the handmaiden of its demise — I don’t know how you can see that as other than tragic.”

An Introduction

Mr. Khalilzad had been out of government for years when, during the 2016 presidential campaign, he introduced Mr. Trump for a foreign policy speech hosted by a think tank with which he was affiliated. A lifelong Republican, Mr. Khalilzad did not endorse Mr. Trump, noting his “provocative views.” But the introduction earned him good will in Mr. Trump’s inner circle.

Then, in 2018, Mr. Khalilzad told officials in the Trump administration that Taliban representatives were interested in talking about a peace agreement. That September, Secretary of State Mike Pompeo appointed him envoy for “the singular mission” of “developing the opportunities to get the Afghans and the Taliban to come to a reconciliation.”

In practice, however, the talks focused on the terms of the U.S. withdrawal that Mr. Trump sought. Eighteen months and hundreds of hours of bartering in Doha, the Qatari capital, produced an agreement in February 2020 under which the United States agreed to withdraw all its troops and the Taliban promised to halt attacks on American forces and never harbor terrorist groups.

The deal also included a Taliban pledge to begin direct talks with the U.S.-backed government in Kabul, as Mr. Pompeo had directed. But the Afghan government was reluctant, and the Taliban seemed unwilling to compromise on their goal to establish a religiously based Islamic emirate.

Critics say Mr. Khalilzad negotiated little more than a relatively safe U.S. retreat.

“I believe Ambassador Khalilzad was too willing to make concessions to the Taliban and to throw the Afghan government under the bus,” said Lisa Curtis, who worked closely with Mr. Khalilzad in the Trump administration as the National Security Council’s senior director for South and Central Asia. “It was clear to many people that the Taliban was not interested in a peace process, but only in pursuing a military path to power.”

Mr. Khalilzad’s supporters say that he was handed an impossible task when he joined the Trump administration.

“I’ve been very critical of the February 2020 agreement that he negotiated,” Mr. Edelman said. “But I will say in his defense: Trump cut the legs out from under it. What kind of negotiating leverage does he have when the president is repeatedly saying, ‘We’re going to get the hell out of Afghanistan!’”

While he defends the agreement, Mr. Khalilzad also argues that the United States lost the will to fight in Afghanistan, partly because of the failures of “my former military colleagues.”