After September 11, 2001, America was forced to go to war in Afghanistan. Al-Qaeda, which had killed nearly 3,000 people inside the United States, was using the central Asian nation as a training ground, and the Taliban refused to oust its guests. Washington needed to degrade the group’s capabilities and punish the government that had given the terrorists sanctuary.

These tasks had been largely completed by December. The United States then had two options. Put serious effort into creating a competent, honest, and strong regime that could survive on its own. Or leave.

Naturally, the Bush administration did neither. Instead, it turned to the neoconservative lobby, which wanted war with Iraq. President George W. Bush kept forces in Central Asia, but not enough to achieve his nation-building ends. The rest of his efforts went into the catastrophic Iraqi misadventure. By President Barack Obama’s administration, Afghanistan was long gone as a viable U.S. protectorate. Yet Obama twice increased American forces there.

Today officials increasingly speak of the war being unwinnable. Even veterans, according to the Pew Research Center, believe that the war “was not worth fighting” and that the U.S. should withdraw. America has wasted many lives and much money attempting to create a democracy in Central Asia, and these sunk costs cannot be redeemed. The only question is whether future benefits will be worth future gains.

President Donald Trump began with a clean slate, having run against his predecessor’s foreign misadventures. “Afghanistan is a complete waste,” businessman Trump declared. “Let’s get out.” But in office, he was besieged by his own appointees and ended up expanding the garrison to about 14,000 service members (other countries contribute nearly 9,000).

Nothing has been achieved by this escalation except more American deaths. Now the president is once again talking about pulling out. In the meantime, his administration is negotiating with the Taliban. Once Washington and the insurgents finish talking, the latter are supposed to make a deal with the U.S.-backed Kabul government.

The negotiations are supposedly going well. The U.S. garrison is reportedly to be drawn down to between 8,000 and 9,000 when the agreement is signed. And that number might fall to zero as soon as October 2020 if the Taliban begins talks with the Kabul government.

The administration is hopeful. America’s Afghan allies are fearful. Domestic critics are apoplectic.

The most obvious question is: how will the accord be enforced? An Afghan official told the Washington Post, “The Americans call this a peace negotiation, but the Taliban definitely perceive it as a withdrawal negotiation.” In fact, the pact is useful primarily for achieving an American exit.

The Afghan government’s ability to stand on its own is doubtful at best. Washington and its allies have spent billions to train Afghan security forces, but a few years back when I visited, trainers were privately skeptical about their mission. The situation has only deteriorated since then.

In August, the Special Inspector General for Afghanistan Reconstruction (SIGAR) found that the strength of the Afghan security forces had fallen by 42,000 since last year and was at only 77 percent of authorized levels. A New York Times analysis concluded that “the Taliban can attack many such bases almost at will.” Few military or police recruits want to sacrifice their lives for the Kabul government. In contrast, Afghanistan’s special operations forces fight well but are too few and are over-stretched even now.

Continued U.S. involvement is no answer. Already Americans have been fighting in Afghanistan longer than the Civil War, Spanish-American War, World War I, World War II, and Korean War combined. Washington’s military commitment peaked in 2011 with 100,000 military personnel, backed by 40,000 more from NATO and other nations. Even then, the U.S. was unable to achieve anything that might resemble victory and there is no political support to move back to those troop levels.

Yet on virtually every measure—areas under insurgent control, security force casualties, Taliban attacks on urban areas, suicide attacks in Kabul, U.S. involvement in combat—the situation continues to worsen. In the capital, American employees have abandoned the streets and now use a helicopter to travel to the airport. Other problems only fester, among them, corruption, drug production, development failures, and political infighting.

Ioannis Koskinas of New America advocates that Washington stick around and use its leverage to get “more out of the Afghan government.” His belief that this will yield sufficient “results in the delivery of governance and security sector reform, as well as demonstrative progress in counter-corruption initiatives” is placing fantastic, irrational hope before lengthy, depressing experience. Indeed, does anyone in Kabul believe that is possible? Michael Semple of Queen’s University recently visited Afghanistan and observed, “The mood in Kabul feels very pre-Saigon,” with people “asking me how to get their family and assets out.”

The alternative to an agreement with zero Americans is not a stable, democratic, successful Afghanistan; but no agreement leaves those 14,000 Americans, enough to help protect Kabul and a few other urban areas, with not much else.

Fighting would continue. Afghanistan would continue to be a Potemkin country. The official government would continue to be ineffective, corrupt, and unloved. The insurgents would gain additional ground. All the while, U.S. personnel would continue to die.

For what?

The most appealing answer is humanitarian. However, America should not send its young men and women to garrison the globe because it is filled with tragedy. Many Afghans, especially women seeking freedom, share a liberal vision for the future. However, the U.S. has also learned at great cost the extraordinary difficulties of international social engineering. The desire to do good does not justify sending others off to war.

The argument most likely to appeal to Americans rightly tired of what the president has called “endless wars” is that these conflicts forestall future terrorist attacks. President Trump has admitted that his aides told him “if we don’t go there, they’re going to be fighting over here.” The permanently hysterical Senator Lindsey Graham just predicted another 9/11 if the U.S. withdraws from Afghanistan.

However, the Taliban has nothing to do with terrorism. It focuses its attention and repression inward. Washington targeted Afghanistan because al-Qaeda was located there, but today the country is home only to the terrorist group’s remnants. Its leader, Osama bin Laden, took refuge in Pakistan next door, where he was killed. The 9/11 operation, as it turns out, was concocted almost everywhere except Afghanistan.

In victory, the Taliban isn’t likely to invite al-Qaeda back in. Taliban officials openly expressed anger at bin Laden for violating his promises and abusing their hospitality by striking America. Their current use of al-Qaeda forces, “which play only a limited role,” according to a recent study by my Cato colleagues John Glaser and Trevor Thrall, is unsurprising. They’re there for the same reason that Washington and Kabul rely on unsavory warlords against the Taliban.

Nor would America’s departure change anything. Al-Qaeda and other terrorist groups are currently in Afghanistan despite America’s presence there. Moreover, al-Qaeda is mostly a franchise with off-shoots located elsewhere, like al-Qaeda in the Arabian Peninsula. The Islamic State is a problem in Afghanistan, too, but its chief enemy is the Taliban. With the U.S. out, the Taliban would be better positioned for the power struggle to come.

Then there are the various predictions of the doom and gloom that will descend on Central Asia after a U.S. withdrawal. Yet even if these are true, they matter little to America. The region is not vital or even relevant to Washington. Central Asia is far closer to China, Europe, India, and Russia. Indeed, more proximate nations, including Iran and Pakistan, have incentives to work to stabilize Afghanistan, whatever factions or regimes might emerge.

Finally, there are the tired warnings about credibility. Yet if Washington decided it could never end a war short of victory, Americans would still be fighting in Korea, Vietnam, and perhaps the War of 1812. Maybe credibility should have been taken into consideration when the U.S. decided to try nation-building in a highly impoverished, radically decentralized, fundamentalist Islamist, and ethnically fractured country on the other side of the globe.

In exiting Afghanistan, Washington should make one commitment: if the Taliban welcome back al-Qaeda or other terrorist organizations, the U.S. will employ “fire and fury.” Victorious insurgents aren’t likely to invite their own destruction.

But beyond that, it is time for America to leave Afghanistan. CNN’s Fareed Zakaria insists that “Washington needs to make sure it doesn’t just end the war but also wins the peace.” But not every problem on earth is Washington’s to solve. The president was right when he declared: “Let’s get out of Afghanistan.” That tragic country’s future should be settled by the Afghans and their neighbors.