“War,” the late French prime minister Georges Clemenceau famously remarked, “is a series of catastrophes that results in a victory.” That is a good way to think about the United States’ odyssey in the “war on terror.” For 20 years, Washington has struggled and mostly failed to reduce the overall level of global terrorism and to create a healthier political climate in the Muslim world. It has also endured slow, grinding quagmires and sharp, humiliating setbacks. Yet on the most fundamental level, the United States has achieved its strategic objective: it has prevented catastrophic attacks against the U.S. homeland, mainly by becoming extremely proficient at destroying terrorists’ sanctuaries and pulverizing their networks.

The United States has paid too high a price for this success. Yet that price has fallen dramatically over time as Washington has developed what is, on balance, a better counterterrorism approach. After conducting unsustainably expensive military commitments in Afghanistan and Iraq, the United States underreached by pulling back from the broader Middle East too fast and allowing old threats to reemerge. But since around 2014, Washington has settled on a medium-footprint model based on modest investments, particularly in special operations forces and airpower, to support local forces that do most of the fighting and dying. When combined with nonmilitary tools such as intelligence cooperation, law enforcement efforts, and economic aid, this approach provides reasonably good protection at a reasonable price.

A medium-footprint strategy is no silver bullet. It offers only incremental and incomplete solutions to the political problems underlying extremist violence. It also necessitates tradeoffs with other priorities, such as competing with China, and is politically vulnerable because of its association with long, frustrating wars. Yet the experience of the past two decades suggests that the medium-footprint strategy is still the best of bad options available to the United States.

SUSTAINABLE COUNTERTERRORISM

The war on terror certainly hasn’t gone as U.S. policymakers would have liked. In the immediate aftermath of 9/11, few would have predicted that the United States would spend two decades fighting in Afghanistan, only to leave with the Taliban on the march; that it would invade Iraq in 2003, withdraw in 2011, and a few years later send troops back to destroy a self-proclaimed caliphate that Washington’s earlier missteps had helped to produce; and that it would spend trillions of dollars and sacrifice thousands of lives in an endless global battle against terror.

On some dimensions, this effort can be simply described as a failure. Overall levels of global terrorism are higher now than they were in 2001. Depending on how one measures, the number of terrorist attacks and people killed by terrorists around the world each year is three to five times as high as it was in 2011, although few of the victims are Americans.

This failure reflects another: the United States has had relatively little success transforming the underlying political conditions in the greater Middle East and in parts of Africa. Across this expansive region, rapidly growing populations, lack of economic opportunity, and legacies of corruption and misrule have bred instability and repression. Mishandled U.S. interventions, especially in Iraq and Libya, have sometimes made the situation worse.

Despite these setbacks, the United States has achieved its most important goal in the war on terror: preventing major mass-casualty attacks on the U.S. homeland. Although Indonesia, Saudi Arabia, Spain, and the United Kingdom all suffered major terrorist attacks in the four years after 9/11 and Europe endured a slew of attacks between 2014 and 2017, the United States has suffered only around 100 fatalities at the hands of jihadi terrorists since 9/11—a tiny fraction of the number of Americans who were murdered by others in the last two decades.

The United States has achieved its most important goal in the war on terror: preventing major mass-casualty attacks on the U.S. homeland.

The United States has protected itself by blending aggressive law enforcement, intelligence, and diplomatic efforts with military operations against the most dangerous jihadi organizations. In Afghanistan, Iraq, Somalia, Syria, and elsewhere, the United States has repeatedly disrupted or destroyed territorial safe havens carved out by the Islamic State (also known as ISIS), al Qaeda, and their offshoots and affiliates. It has also developed an unparalleled ability to decapitate terrorist organizations; decimate their ranks of financiers, facilitators, and operational-level commanders; and keep them under pressure and off balance.

By some estimates, U.S. forces and their international partners have killed or captured 80 percent of al Qaeda leaders and operatives in Afghanistan—even if new leaders have stepped into their place, at least until meeting their own demises as well. How exactly the United States has managed to prevent a major terrorist attack on U.S. soil over the last two decades remains a hotly debated question, but one answer, clearly, is that Washington has inflicted devastating losses on its enemies and forced them to focus more on surviving than thriving.

This success came at a much higher price than most policymakers initially expected—by a conservative estimate, some $4 trillion in direct and indirect costs, 7,000 U.S. military fatalities, and the diversion of government attention away from other foreign policy priorities. But the rate of expenditure has come down markedly in the last decade. Since 2015, the number of U.S. service members killed in combat has been in the low dozens or less each year, compared with the high hundreds at the peak of the wars in Iraq and Afghanistan. And whereas those wars once cost as much as $200 billion a year in all, the annual cost of the U.S. campaign against ISIS from 2014 to 2019 was just a few billion dollars. The entire U.S. military presence in the broader Middle East, which covers counterterrorism and other priorities such as deterring Iran, now runs between $50 billion and $60 billion annually—about a third of its peak levels during the latter Bush and early Obama years.  

Just as important, the war on terror is no longer a bleeding strategic or diplomatic wound. And as Washington has scaled back its military presence in the broader Middle East, it has been able to focus more on other priorities. In short, the war on terror does not cost what it once did, mainly because the United States has found a more sustainable approach—one that emphasizes managing intractable problems rather than solving them or simply walking away.

MOWING THE GRASS

This strategy was born of trial and error. In the decade after 9/11, the United States found that heavy-footprint interventions such as those in Iraq and Afghanistan were a recipe for military and strategic exhaustion. But too light a counterterrorism footprint could invite catastrophic reversals. When the United States withdrew completely from Iraq in 2011 while also drawing down counterterrorism operations elsewhere, it created dangerous security vacuums. In particular, the pullout from Iraq, coupled with the chaos created by civil war in Syria, fueled the rise of ISIS, which conquered territory in Iraq and Syria and destabilized vast swaths of the Middle East.

The upshot was a medium-footprint strategy, meant to be both aggressive and limited. This strategy involved the direct use of U.S. military power—especially special operations forces, drones, and manned airpower—against ISIS and other prominent terror groups. But it wielded these and other tools (such as training and advisory missions, intelligence, and logistics) primarily to empower local forces that could clear and hold terrain.

In the struggle against ISIS, for example, the Iraqi security forces, Baghdad’s elite Counter-Terrorism Service, and a motley crew of Kurdish and Arab allies in Syria provided the vast majority of the ground forces that fought on the American side. The Pentagon simultaneously adopted a similar approach in Afghanistan, using a combination of direct military action and support for government forces to target al Qaeda (and, later, ISIS) while keeping the Taliban in check.

The medium-footprint strategy was more sustainable and effective than anything Washington had tried before.

This approach allowed the United States to maintain the regional military footholds needed to keep pressure on extremist groups and outsource the heaviest human and military costs to partners and allies. It also leveraged unique U.S. advantages, such as drones and special operations forces, to enable much larger military campaigns. And it dialed back unrealistic political expectations for host countries, promising only marginal improvements, such as empowering less sectarian leaders in Iraq, as potential down payments on deeper reform once conditions stabilized. On the whole, the medium-footprint strategy was more sustainable and effective than anything Washington had tried before.

It also had plenty of problems, of course. In Afghanistan, the strategy could not break the stalemate with the Taliban: at best, it kept pressure on al Qaeda and ISIS and prevented the Taliban from defeating the government. In Syria, the U.S. approach could not solve the underlying problems posed by a vicious civil war. Nor could it spur the dramatic improvements in political stability and effective governance that would have allowed the United States to safely disengage from contested areas. The medium-footprint approach is akin to what Israeli leaders call “mowing the grass”—it delivers results only if repeated indefinitely.

That need for persistence has come to seem more burdensome over time, as U.S. President Joe Biden’s decision to withdraw from Afghanistan confirmed. The pull of the Indo-Pacific has grown stronger as U.S.-Chinese competition has intensified. Because the initial costs of the war on terror were so high, moreover, it has become difficult to sustain even much-reduced military commitments without provoking charges of perpetuating pointless “forever wars.” The experience of witnessing a largely futile troop surge in Afghanistan in 2009 appears to have weighed on Biden’s decision to terminate a less onerous military mission there today, just as the tragic early years in Iraq seemed to influence President Barack Obama’s decision to withdraw all U.S. troops from that country in 2011.

PLAYING THE LONG GAME

These competing priorities and costs of persistence are real, but they are not reasons for Washington to abandon its current counterterrorism approach. For one thing, the tradeoff between counterterrorism and great-power competition is neither zero-sum nor unmanageable. The military commitments required to sustain progress in the counterterrorism fight are relatively modest. They typically involve a few thousand troops in a given country, most of whom do not see ground combat on a regular basis, supported by airpower capable of delivering thousands of strikes a year in certain circumstances. These troop and resource commitments do not meaningfully detract from the United States’ ability to project power into Asia, and the broader U.S. military presence in the Middle East actually provides leverage over China, giving Washington the ability to choke off Beijing’s energy supplies in the event of war and thereby bolstering deterrence.

Moreover, the United States needs a minimum level of stability in the greater Middle East—and a minimum level of safety from terrorist threats—to focus properly on the challenge from China and Russia. Without these, it risks the dreaded “yo-yo effect,” whereby withdrawal leads to surging threats that then require renewed intervention at a higher price. That is a formula for failure in counterterrorism and great-power competition alike.

The history of the past 20 years suggests that the United States must pace itself. Overextension inevitably leads to frustration and the dissipation of limited resources. Yet outright withdrawal can jeopardize counterterrorism and regional security interests that are still important to American voters and to U.S. global strategy. So long as the jihadi threat persists in its current form, the United States needs a counterterrorism approach that allows it to avoid exhausting interventions and damaging retreats.

Finally, the United States has little choice but to play a very long game with respect to political reform. Without greater political inclusion and stability in the Muslim world, there will be no escaping the cycle of threats and response that has trapped the last three U.S. presidents. But as the United States learned in Afghanistan and Iraq, seeking to dramatically accelerate the pace of change involves enormous risks and costs. The only reasonable approach is to promote constructive improvement at the margins, while recognizing that the primary impetus for reform must come from within Muslim societies themselves. This strategy requires patience, but as the history of the Cold War demonstrated, the United States has the capacity for more strategic patience than pundits sometimes give it credit for.

The medium-footprint strategy is not an ideal solution to the ongoing problem of jihadi terrorism. But there is no ideal solution. Perhaps the two most important lessons of the past 20 years are that all of the United States’ counterterrorism options are imperfect, and that as bad as things seem in the greater Middle East, they can always get worse. As the United States reaches a generational milestone in the war on terror, it should acknowledge what has gone wrong—but also preserve the strategy that has allowed it to get a fair amount right.

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  • HAL BRANDS is Henry A. Kissinger Distinguished Professor of Global Affairs at the Johns Hopkins School of Advanced International Studies, a Resident Scholar at the American Enterprise Institute, and a Bloomberg Opinion columnist.
  • MICHAEL O’HANLON is a Senior Fellow and Director of Research at the Brookings Institution’s Foreign Policy Program and the author of The Senkaku Paradox: Risking Great Power War Over Small Stakes.
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