This Q&A with Allen S. Weiner was originally published on the Stanford Law School website.

As the Taliban’s forces closed in on Kabul on Sunday, August 15, 2021, the Afghan President Ashraf Ghani left his country, the acting U.S. ambassador was evacuated, the American flag on the embassy in the country’s capital lowered—and the Biden administration’s plans for an orderly withdrawal of troops, diplomats, and Afghan aids and translators by the anniversary of 9/11 dashed as a scramble for the door becomes more chaotic. After twenty years, 2 trillion dollars, and the lives of almost 2,500 American personnel lost, President Biden said it was time to let the Afghan government and military stand on its own. Here, Stanford Law national security law expert Allen Weiner, who is a research affiliate at FSI’s Center for Democracy, Development and the Rule of Law, and the Center for International Security and Cooperation, discusses the U.S. mission to Afghanistan, its withdrawal, and potential consequences.

What was the American/NATO objective when we invaded Afghanistan almost twenty years ago?

The immediate United States objective at the time of the 2001 invasion was to destroy Al Qaeda’s base of operations in Afghanistan and to kill or capture senior Al Qaeda leaders there.  As those of us who are old enough to remember will recall, the invasion (“Operation Enduring Freedom”) was the U.S.-led response to the 9/11 attacks against World Trade Center twin towers and the Pentagon that were carried out by Al Qaeda. Because the Taliban regime in Afghanistan had a symbiotic relationship with—and provided a safe haven to—Al Qaeda on Afghanistan’s territory, the U.S. and its NATO allies also sought to drive the Taliban from power. At the time, the Taliban was fighting a civil war in Afghanistan and by October 2001 had achieved effective control over most of the country. President Bush and others quickly began to emphasize an additional objective for overthrowing the Taliban— to liberate the Afghan people from the regime’s repressive practices. We sought to promote basic human rights and to end the Taliban’s oppression of women.

Were those objectives met?

The U.S. and its NATO allies largely met those initial goals. Al Qaeda’s training camps in Afghanistan were destroyed, many of its leaders were killed and captured (although some, including Osama bin Laden, managed to escape at least initially), and its ability to plan, finance, and execute major global terrorist operations was severely diminished. U.S. and NATO forces drove the Taliban from power, and after a transitional period, a new government led by Hamid Karzai was established. Women and girls resumed participation in public life in Afghanistan, including education.

But those successes were fleeting?

As we know, the successes did not last. Although Al Qaeda never resumed significant operations in Afghanistan, the organization metastasized, and lethal variants of the organization arose in Yemen, Iraq and Syria, and the Maghreb, among other places. Other terrorist groups, such as the Islamic State and al Shabaab, either grew out of or have affiliations of varying degrees of intensity with Al Qaeda. We have also seen attacks carried out by homegrown terrorist organizations with only loose affiliations to Al Qaeda, sometimes only ideological affinities. So, while Operation Enduring Freedom significantly disrupted terrorist operations originating from Afghanistan, it cannot be said to have eliminated the threat of transnational terrorism.

And the Taliban continued to be a simmering problem in Afghanistan, didn’t it?

The goal of eradicating the Taliban, obviously, also was unmet. Although then Secretary of Defense Donald Rumsfeld declared an end to major combat operations against Al Qaeda and the Taliban in May 2003, a revitalized Taliban renewed an intense civil war in the summer of  2006. That civil war against the Afghanistan government—which appears now to have been won by the Taliban—continued with varying degrees of intensity until the past few days. And if another of the goals of the invasion was to improve the protection of human rights in Afghanistan, we must recognize that civilians suffered terribly during the civil war.

Are there any (hopefully) enduring successes from the twenty-year investment by the U.S. and NATO?

Afghanistan did make significant progress in terms of economic development and the realization of at least some civil and political rights. Per capita GDP rose dramatically in the decades after the U.S. invasion. The status of women and girls improved along many dimensions, including health, life expectancy, education levels, and participation in government institutions. The Taliban’s victory clearly imperils these gains.

The Trump Administration negotiated an agreement with Taliban in 2020 providing for the withdrawal of U.S. Forces from Afghanistan by May 2021, as part of which the Taliban promised not to deliberatively attack U.S. troops during the withdrawal period.  Since then, the Taliban has been steadily gaining control over provinces in the county, and civilian casualties have been rising. Was it pure fantasy that the US was maintaining the peace?

The Trump Administration’s February 2020 agreement with Taliban, in which the U.S. promised to withdraw its forces from Afghanistan in a little over a year, even though the Taliban did not agree to even a ceasefire, much less reach any political agreements with the government about ending the civil war, was the beginning of the end. It clearly signaled to both the Taliban and the government that the U.S. was now concerned only with the security of its own forces, and that the Afghan government was on its own. Given that the Taliban was making progress in gaining territory, at least in the countryside, even with U.S. troops present, many analysts—including the U.S. intelligence community—forecast the eventual overthrow of the Afghan government. It is only the shocking speed with which that happened that is a real surprise.

The fall of the Afghan government has taken many, including apparently some in the Biden administration, by surprise. Why did the collapse of the Afghan military happen so swiftly?  And what role did the Afghan police force and corruption play?

Many commentators who have been critical of the U.S. effort to build up the Afghan military have long expressed doubts about the effectiveness of the Afghanistan National Defense and Security Forces (ANDSF), and many analysts predicted that the Taliban would ultimately prevail against the government after the U.S. and its NATO allies withdrew from Afghanistan. That said, I don’t think anyone predicted it would happen as swiftly as it did.

Multiple factors have been cited to explain how the Taliban—a force estimated to comprise some 75,000 fighters—defeated the 300,000-member strong ANDSF. First, despite the seeming superiority of the government forces, conditions for ANDSF soldiers were quite abysmal. Many reportedly went months without being paid. They lacked ammunition and even food. There are reports of incompetent leadership within the armed forces, leaving Afghan soldiers exposed in the middle of pitch battles, without reinforcements.

A second factor is the pervasive and corrosive corruption among Afghan government actors.  This helps explain why—despite the U.S. infusion of billions of dollars in military assistance— Afghan soldiers went without pay and lacked adequate ammunition.  It also explains why in some cases, after Afghan forces fighting alongside U.S. forces succeeded in clearing territory of Taliban insurgents, the Afghan government would fail to hold it. The notoriously corrupt and unprofessional Afghanistan police forces—who were in charge of security after territory had been cleared of Taliban fighters by the ANDSF—reportedly engaged in predatory practices targeting the local community or could be bought off by the insurgency to cede ground back.

Third, some critics of the U.S. effort to modernize the Afghan army have long argued that the ANDSF lacked resolve to aggressively engage the Taliban insurgency in the absence of active support from U.S. soldiers. Although there are many stories of Afghan soldiers fighting fiercely, there are anecdotal accounts of Afghan armed forces engaging in “mini non-aggression deals” with Taliban fighters in their area of responsibility in an effort to avoid armed engagement.

Fourth, the lack of motivation of Afghan armed forces was exacerbated in recent years by the unpopularity and perceived fecklessness of the Afghan government led by President Ashraf Ghani. Re-elected in 2019 after an election with sharply disputed results, in which voter turnout was less than 20 percent, the Ghani government was widely seen as ineffective in addressing corruption, effectively managing the country, or confronting the growing security threat posed by the Taliban. It became a common refrain among Afghan soldiers that the Ghani government was not one worth fighting for.

Fifth, it appears that in at least some provinces in Afghanistan, the Taliban, in essence, offered government forces negotiated settlements to cede control of territory. In some cases, this involved offering payments to government soldiers to switch sides—a particularly attractive offer for soldiers who had not been paid in months. It is likely that the Taliban offered broader commitments, e.g., not to engage in retribution against government soldiers who abandoned the fight, although I have not yet seen reports of such deals.

Sixth, there a seasonal calendar to armed conflict in Afghanistan, and the Taliban has typically engaged in its major military operations during the spring and summer.  Delaying the U.S. withdrawal by six months, so that U.S. forces did not leave during the height of what is known in Afghanistan as “fighting season,” might have given the ANDSF more time to prepare to defend Afghanistan’s cities. Although given how swiftly Afghan government forces were swept aside, this now seems doubtful to me.

Finally, from an operational standpoint, the U.S. has invested billions of dollars in Afghanistan to attempt to build up a military that functions in ways that resemble how a NATO army operates, with air power and advanced weaponry. Such a military depends on extremely complex behind-the-scenes logistics arrangements. In Afghanistan, these logistics systems depended heavily on U.S. contractors, who also began withdrawing from the country after President Biden announced the U.S. withdrawal. Many of the aircraft in Afghanistan’s air force, for instance, were grounded because they lacked parts needed for repairs or routine servicing. One of the lessons of the defeat of the ANDSF is that building a foreign country’s military also requires developing indigenous logistics capacity.

Troops had been drawn down to about 3,000 and negotiations that excluded the Afghan gov’t were conducted with the Taliban during the Trump administration. Could Biden, realistically, have rewound the clock–bringing more troops back? Was Biden pushed into a tough corner?

Although the withdrawal agreement the Trump Administration concluded with the Taliban in February 2020 may not have initiated the death spiral for the Afghanistan government and military, it certainly catalyzed it, as I noted above. It did put the Biden Administration in a tough position; the only option would have been to renege on the agreement, leave U.S. troops in Afghanistan, and to seek to renegotiate the agreement. That said, although that may have been a tough position, it was not an impossible one, as evidenced by the fact that the Biden Administration unilaterally changed the agreed upon date by which U.S. forces would withdraw from Afghanistan from May to August.

I’m not a military strategist, so I can’t say whether maintaining a force of 3,000 U.S. troops in Afghanistan would have changed the military situation on the ground. But I think if the U.S. had said that it would not withdraw the U.S. military presence until there was a ceasefire and the Taliban and the Afghan government have negotiated a power sharing agreement/end to the civil war, that might have changed the Taliban’s political assessment about how to proceed. I stress that this only “might” have changed the Taliban’s thinking. The fact that the Taliban has been fighting for twenty years suggests that the group was very determined to regain control of Afghanistan and re-establish its vision of life for the Afghan people.

I understand that Russia and other countries have negotiated agreements to ensure the safety of their embassies and diplomatic staff so that they can continue operations in Kabul. Have the Americans done the same? If not, how significant will that be for the future safety of the U.S and the threat of terrorism? Will we have “eyes on the ground” and intelligence sources?

The United States is currently withdrawing all of its diplomatic personnel from Afghanistan and will presumably once again shutter its embassy in Kabul. The U.S. will face a difficult question about whether to recognize the new Taliban regime that will be installed in Afghanistan, and if so, whether to resume diplomatic relations and re-open its embassy. If the Taliban regime pursues the policies that characterized its period of rule in the late 1990s, particularly the severe repression of women and girls, I doubt the U.S. will re-establish relations. Even if the U.S. did re-establish diplomatic relations, it is inconceivable that the Taliban would permit the United States to maintain the large intelligence and security presence we have had in Afghanistan over the past two decades. So, we will not have the ability gather intelligence on the ground or to conduct military operations against any terrorist threats that emerge in Afghanistan.

The Taliban has pledged that it will not allow Afghanistan’s territory to be used by terrorist groups that seek to conduct hostile operations against foreign countries. Although the Taliban learned in 2001 about the potential costs to it of harboring such groups on Afghanistan’s territory—namely, being overthrown by the U.S. and its NATO allies—there are obviously reasons to question the Taliban’s promise.

Is there anything Biden can do now to minimize the damage?

The Biden administration does not have much leverage at this point. The administration will presumably signal to the Taliban that it will closely monitor its conduct with respect to preventing its territory from being used by terrorist groups and its performance on human rights issues, including the treatment of women and girls. Should the Taliban perform poorly on these issues, the U.S. could try to secure sanctions against the Taliban regime through the Security Council; after all, the Council had imposed sanctions on the Taliban in the 1990s in response to its providing a safe haven to Osama bin Laden and its violation of human rights, particularly discrimination against women and girls. Today, however, it is unclear whether Russia and China, which are likely to seek stable relations with the Taliban government, would support such sanctions. That means the U.S. would probably be limited to unilateral sanctions as a way of signaling disapproval of, and seeking to change the behavior of, a prospective Taliban government.

In her recent Foreign Affairs essay, The Taiwan Temptation: Why Beijing Might Resort to Force, Center Fellow Oriana Skylar Mastro argues that Chinese leaders now consider a military campaign to take Taiwan a real possibility and cautions that the United States cannot by itself alter Beijing’s calculus on Taiwan. The essay sparked a heated debate. In the September/October issue of Foreign Affairs, several scholars — Rachel Esplin Odell and Eric Heginbotham, Bonny Lin and David Sacks, and Kharis Templeman — provide counterarguments to Mastro's analysis and she responds to their criticism. Read her complete rebuttal below.

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Rachel Esplin Odell and Eric Heginbotham, Bonny Lin and David Sacks, and Kharis Templeman all argue that China is unlikely to attempt armed unification with Taiwan. Although I appreciate their perspectives, they do not present any new evidence that would make me reconsider my assessment that the risk of Chinese aggression across the Taiwan Strait is real and growing. To the contrary, they repeat many of the increasingly dangerous misperceptions that I sought to dispel in my original article—namely, that China does not have the military capabilities to pull off an amphibious invasion, that the economic costs of an invasion would be sufficient to deter Chinese President Xi Jinping, and that China can afford to wait indefinitely to achieve its most important national goal of unification. My critics assume that insofar as there are risks, they can be dealt with through relatively limited adjustments in U.S. policy and military posture — a position with which I still strongly disagree. 

Let’s take these arguments in order. My critics say that I have exaggerated China’s military capabilities and understated the difficulties of an invasion. But their assessments rely on outdated or largely irrelevant comparisons. Odell and Heginbotham, for instance, note that the United States needed more naval tonnage to capture Okinawa from Japan in 1945 than China has today. But this example is inapposite. Japan’s military was more than six million strong in 1945 and had been fighting for over a decade; Taiwan’s military consists of 88,000 personnel and two million reservists, of whom only 300,000 are required to complete even a five-week refresher training course. Tonnage, moreover, is not a useful metric. Modern navies have moved to lighter, more flexible fleets. Odell and Heginbotham point out that civilian ships were of only limited use in the Falklands War, but the United Kingdom used just 62 of them in that campaign. The People’s Armed Forces Maritime Militia has many thousands of ships and is closer to a naval force than a civilian one. If China were to mobilize all its naval vessels, including its new large amphibious transport ships and civilian ships, it could hypothetically carry hundreds of thousands of troops across the 80-mile-wide Taiwan Strait in a short period of time. Even if the United States had enough warning to optimally position its submarines, it does not have enough munitions to target such a large force. 

For their part, Lin and Sacks argue that to believe China can take Taiwan by force is to fall for a Chinese misinformation campaign. They warn that “analysts should not accept at face value China’s claim that it could easily win a fight against Taiwan.” But no one, not even the cockiest of People’s Liberation Army analysts, argues that a full-scale attack on Taiwan would be easy, only that the PLA could prevail at an acceptable cost. Moreover, my assessment of Chinese military capabilities is not based on Chinese discourse or the results of war games alone. Reams of unbiased and rigorous analysis—from the U.S. Department of Defense’s annual report to Congress on China’s military modernization to Congressional Research Service reports on Chinese naval modernization to hundreds of studies by think tanks and defense-affiliated organizations, such as the RAND Corporation—suggest that the PLA has made unparalleled advances in the past two decades and could take on the United States in certain scenarios. Indeed, Heginbotham himself argued in 2017 that “the balance of power between the United States and China may be approaching a series of tipping points, first in contingencies close to the Chinese coast (e.g., Taiwan).” 

I do not mean to suggest that a Chinese invasion would be a cakewalk. Taiwan could get some shots in, but it does not have the ability to defend itself. Luckily, the United States would, I believe, come to Taiwan’s aid and could still prevail in many scenarios. Taiwan is far from a lost cause. But ten years ago, the United States would have prevailed in any scenario. Because there are now some scenarios in which U.S. strategists think the United States could lose, it is not unfathomable to think that Chinese strategists have come to a similar conclusion. 

My critics also argue that economic considerations will deter Beijing. Should China attempt to use force to assert control over Taiwan, the international response would be severe enough to imperil Xi’s ambitious development goals. But as I argued in my original article, Chinese analysts have good reason to think the international response would be weak enough to tolerate. China could even reap economic benefits from controlling Taiwan, whose manufacturers accounted for more than 60 percent of global revenue from semiconductors last year. The United States is heavily reliant on Taiwanese semiconductors. Should China take Taiwan, it could conceivably deprive the United States of this technology and gain an economic and military advantage. 

But economic costs or benefits, while part of Beijing’s calculus, are unlikely to be the determining factor. Xi’s top priority is protecting China’s sovereignty and territorial integrity—as Beijing defines it. China’s Belt and Road Initiative, its militarization of the South China Sea, and its sanctions against countries that offend it, such as Australia or South Korea, all demonstrate that Chinese leaders are willing to subordinate economic considerations to considerations of power and prestige. In a speech marking the 100th anniversary of the Chinese Communist Party in July, Xi warned against foreign attempts to bully or oppress China, declaring that “anyone who dares try to do that will have their heads bashed bloody against the great wall of steel forged by over 1.4 billion Chinese people.” Those words should be taken seriously. 

Finally, my critics argue that China has no need to attempt to forcibly unify with Taiwan. Lin and Sacks think peaceful unification is working; Templeman believes China can wait indefinitely to resolve the issue. I disagree because I think unification is a top priority for the Chinese Communist Party and Taiwan will not give up its autonomy without a fight. 

A Chinese invasion is by no means imminent or inevitable, but Beijing is now seriously considering initiating a conflict to gain political control over Taiwan, whereas in the past the only scenario in which it would have used force was to prevent Taipei from declaring independence. I agree with Templeman that China is unlikely to invade in the next four years (although I think this is largely because China could benefit from more time to prepare, not because it fears U.S. President Joe Biden’s resolve), but his argument that China can wait indefinitely is logically and empirically flawed. As I argued in my original article, Xi has made numerous statements that suggest he wants to achieve unification during his reign. It would be unwise to dismiss these as mere rhetoric, since he has repeatedly voiced his intention to assert control over other territorial claims before doing exactly that — in the South China Sea, by building military infrastructure and conducting naval drills, and in Hong Kong, by imposing a harsh national security law last year.

Templeman argues that if China believes the United States is in decline, then it has every reason to wait on Taiwan. But in the eyes of Chinese strategists, American decline actually hastens the need for action. Power transition theory, which holds that war becomes more likely as the gap between a rising power and an established great power diminishes, is also studied in Beijing. And although U.S. strategists fret that a rising China, dissatisfied with the U.S.-led international order, will become aggressive and start a conflagration, Chinese strategists fear a different pathway to war. They worry that the United States, unable to accept its inevitable decline, will make a dangerous last-ditch effort to hold on to its unrivaled great-power status. By this logic, a declining United States is more dangerous than a stable, ascendant one. 

Lin and Sacks make a different argument for why Beijing does not need to attempt armed unification. They believe that Chinese leaders remain committed to their long-standing approach of limited coercion coupled with economic incentives showcasing the benefits of unification because that strategy is working. As evidence of Beijing’s progress, Lin and Sacks point to polling that shows the majority of people in Taiwan support the status quo, not independence. But it is an enormous leap from not supporting independence to desiring or conceding to unification. As Lin and Sacks themselves acknowledge, China has employed this strategy of limited coercion and economic inducements for decades, but Taiwan is no closer to being a part of mainland China. In a September 2020 poll conducted by National Chengchi University, only six percent of Taiwanese citizens preferred eventual or immediate unification. So although Lin and Sacks are correct that Beijing will likely continue with its carrot-and-stick approach, it will still need to put boots on the ground to gain full political control of Taiwan. 

My critics also raise concerns about some of the policy implications of my argument. Odell and Heginbotham warn against focusing too much on the credibility of the U.S. military threat when it comes to deterrence, rightly highlighting the equal importance of reassurance. They warn that changes in U.S. policy toward Taiwan could convince Beijing that the United States now supports Taiwanese independence — a misperception that could lead to war. But my argument is for a change in posture, not in policy: the United States should develop the force posture and operational plans to deny China its objective in Taiwan and then credibly reveal these new capabilities. It should not make dangerous policy changes that would risk provoking a Chinese military response. Indeed, I have argued elsewhere that even if a war breaks out over Taiwan and the United States wins, Washington should not demand Taiwan’s independence as one of the terms of peace. 

Templeman raises a separate concern: that highlighting the potential costs of defending Taiwan could bolster the case of those advocating that Washington abandon Taipei. If this were a serious worry, I would be the first to shift my work to more private channels. But those calling for the United States to reconsider its commitment to defend Taiwan are still in the minority, and the Biden administration has been clear that it would come to Taiwan’s aid in the event of an invasion.

Moreover, the reaction of the U.S. Department of Defense to the threat posed by China’s growing military power has been not to back down but to ramp up efforts to counter it. From new doctrines that enhance joint capabilities between the U.S. Air Force and the U.S. Navy to base-resilience initiatives to efforts to improve U.S. early warning systems in the region, the Pentagon is firing on all cylinders to ensure it can deter and, if necessary, defeat China in a wide range of conflict scenarios. U.S. Cyber Command, the U.S. Space Force, and the Department of Defense’s Joint Artificial Intelligence Center were all established partly to counter Chinese advantages in those organizations’ respective domains. If Lin and Sacks are correct that China exaggerates its capabilities to try to convince the United States to give up, Beijing has achieved the opposite.   

In the end, all my critics highlight an important truth: the situation across the Taiwan Strait has been relatively stable for 70 years because of the United States. Washington has managed to convince Beijing that armed unification would fail and that China would pay a hefty price for trying. But China is not the same country it was 70 years ago. Its rapid military modernization, spectacular economic ascent, and growing global influence have changed Beijing’s calculus on many issues. It has taken a more assertive approach to international institutions; built one of the world’s largest, most capable militaries; and extended its economic influence deep and far throughout the world. It would be wishful thinking to assume that China has not also changed its thinking on Taiwan.

Indeed, although my critics argue that China is unlikely to invade, they still recommend that Taiwan improve its defenses and that the United States enhance its military posture in the region — not exactly a vote of confidence in Beijing’s restraint. I had hoped to convince skeptics that China is now seriously considering armed unification, but at least our debate has yielded a consensus that more must be done in Taipei and Washington to enhance deterrence across the Taiwan Strait.