The war-weary United States, for which the phrase “boots on the ground” has become politically toxic, prefers to eliminate its terrorist foes from the skies. The tool of choice: unmanned aerial vehicles, also known as drones. In Pakistan, Somalia, and Yemen -- often far away from any battlefield where American troops are engaged -- Washington has responded to budding threats with targeted killings.

Like any other weapon, armed drones can be tactically useful. But are they helping advance the strategic goals of U.S. counterterrorism? Although terrorism is a tactic, it can succeed only on the strategic level, by leveraging a shocking event for political gain. To be effective, counterterrorism must itself respond with a coherent strategy. The problem for Washington today is that its drone program has taken on a life of its own, to the point where tactics are driving strategy rather than the other way around.

The main goals of U.S. counterterrorism are threefold: the strategic defeat of al Qaeda and groups affiliated with it, the containment of local conflicts so that they do not breed new enemies, and the preservation of the security of the American people. Drones do not serve all these goals. Although they can protect the American people from attacks in the short term, they are not helping to defeat al Qaeda, and they may be creating sworn enemies out of a sea of local insurgents. It would be a mistake to embrace killer drones as the centerpiece of U.S. counterterrorism.

AL QAEDA’S RESILIENCE

At least since 9/11, the United States has sought the end of al Qaeda -- not just to set it back tactically, as drones have surely done, but also to defeat the group completely. Terrorist organizations can meet their demise in a variety of ways, and the killing of their leaders is certainly one of them. Abu Sayyaf, an Islamist separatist group in the Philippines, lost its political focus, split into factions, and became a petty criminal organization after the army killed its leaders in 2006 and 2007. In other cases, however, including those of the Shining Path in Peru and Action Directe in France, the humiliating arrest of a leader has been more effective. By capturing a terrorist leader, countries can avoid creating a martyr, win access to a storehouse of intelligence, and discredit a popular cause.

Despite the Obama administration’s recent calls for limits on drone strikes, Washington is still using them to try to defeat al Qaeda by killing off its leadership. But the terrorist groups that have been destroyed through decapitation looked nothing like al Qaeda: they were hierarchically structured, characterized by a cult of personality, and less than ten years old, and they lacked a clear succession plan. Al Qaeda, by contrast, is a resilient, 25-year-old organization with a broad network of outposts. The group was never singularly dependent on Osama bin Laden’s leadership, and it has proved adept at replacing dead operatives.

Drones have inflicted real damage on the organization, of course. In Pakistan, the approximately 350 strikes since 2004 have cut the number of core al Qaeda members in the tribal areas by about 75 percent, to roughly 50–100, a powerful answer to the 2001 attacks they planned and orchestrated nearby. As al Qaeda’s center of gravity has shifted away from Pakistan to Yemen and North Africa, drone strikes have followed the terrorists. In September 2011, Michael Vickers, the U.S. undersecretary of defense for intelligence, estimated that there were maybe four key al Qaeda leaders remaining in Pakistan and about ten or 20 leaders overall in Pakistan, Somalia, and Yemen.

Drones have also driven down the overall level of violence in the areas they have hit. The political scientists Patrick Johnston and Anoop Sarbahi recently found that drone strikes in northwestern Pakistan from 2007 to 2011 resulted in a decrease in the number and lethality of militant attacks in the tribal areas where they were conducted.

Such strikes often lead militants simply to go somewhere else, but that can have value in and of itself. Indeed, the drone threat has forced al Qaeda operatives and their associates to change their behavior, keeping them preoccupied with survival and hindering their ability to move, plan operations, and carry them out. The fighters have proved remarkably adaptable: a document found left behind in February 2013 by Islamist fighters fleeing Mali detailed 22 tips for avoiding drone attacks, including using trees as cover, placing dolls and statues outside to mislead aerial intelligence, and covering vehicles with straw mats. Nonetheless, the prospect of living under the threat of instant death from above has made recruitment more difficult and kept operatives from establishing close ties to local civilians, who fear they might also be killed.

But the benefits end there, and there are many reasons to believe that drone strikes are undermining Washington’s goal of destroying al Qaeda. Targeted killings have not thwarted the group’s ability to replace dead leaders with new ones. Nor have they undermined its propaganda efforts or recruitment. Even if al Qaeda has become less lethal and efficient, its public relations campaigns still allow it to reach potential supporters, threaten potential victims, and project strength. If al Qaeda’s ability to perpetuate its message continues, then the killing of its members will not further the long-term goal of ending the group.

Not only has al Qaeda’s propaganda continued uninterrupted by the drone strikes; it has been significantly enhanced by them. As Sahab (The Clouds), the propaganda branch of al Qaeda, has been able to attract recruits and resources by broadcasting footage of drone strikes, portraying them as indiscriminate violence against Muslims. Al Qaeda uses the strikes that result in civilian deaths, and even those that don’t, to frame Americans as immoral bullies who care less about ordinary people than al Qaeda does. And As Sahab regularly casts the leaders who are killed by drones as martyrs. It is easy enough to kill an individual terrorist with a drone strike, but the organization’s Internet presence lives on.

A more effective way of defeating al Qaeda would be to publicly discredit it with a political strategy aimed at dividing its followers. Al Qaeda and its various affiliates do not together make up a strong, unified organization. Different factions within the movement disagree about both long-term objectives and short-term tactics, including whether it is acceptable to carry out suicide attacks or kill other Muslims. And it is in Muslim-majority countries where jihadist violence has taken its worst toll. Around 85 percent of those killed by al Qaeda’s attacks have been Muslims, a fact that breeds revulsion among its potential followers.

The United States should be capitalizing on this backlash. In reality, there is no equivalence between al Qaeda’s violence and U.S. drone strikes -- under the Obama administration, drones have avoided civilians about 86 percent of the time, whereas al Qaeda purposefully targets them. But the foolish secrecy of Washington’s drone program lets critics allege that the strikes are deadlier and less discriminating than they really are. Whatever the truth is, the United States is losing the war of perceptions, a key part of any counterterrorism campaign.

Since 2010, moreover, U.S. drone strikes have progressed well beyond decapitation, now targeting al Qaeda leaders and followers alike, as well as a range of Taliban members and Yemeni insurgents. With its so-called signature strikes, Washington often goes after people whose identity it does not know but who appear to be behaving like militants in insurgent-controlled areas. The strikes end up killing enemies of the Pakistani, Somali, and Yemeni militaries who may not threaten the United States at all. Worse, because the targets of such strikes are so loosely defined, it seems inevitable that they will kill some civilians. The June 2011 claim by John Brennan, President Barack Obama’s top counterterrorism adviser at the time, that there had not been a single collateral death from drone attacks in the previous year strained credulity -- and badly undermined U.S. credibility.

The drone campaign has morphed, in effect, into remote-control repression: the direct application of brute force by a state, rather than an attempt to deal a pivotal blow to a movement. Repression wiped out terrorist groups in Argentina, Brazil, Peru, and tsarist Russia, but in each case, it sharply eroded the government’s legitimacy. Repression is costly, not just to the victims, and difficult for democracies to sustain over time. It works best in places where group members can be easily separated from the general population, which is not the case for most targets of U.S. drone strikes. Military repression also often results in violence spreading to neighboring countries or regions, which partially explains the expanding al Qaeda footprint in the Middle East and North Africa, not to mention the Caucasus.

KEEPING LOCAL CONFLICTS LOCAL

Short of defeating al Qaeda altogether, a top strategic objective of U.S. counterterrorism should be to prevent fighters in local conflicts abroad from aligning with the movement and targeting the United States and its allies. Military strategists refer to this goal as “the conservation of enemies,” the attempt to keep the number of adversaries to a minimum.

Violent jihadism existed long before 9/11 and will endure long after the U.S. war on terrorism finally ends. The best way for the United States to prevent future acts of international terrorism on its soil is to make sure that local insurgencies remain local, to shore up its allies’ capacities, and to use short-term interventions such as drones rarely, selectively, transparently, and only against those who can realistically target the United States.

The problem is that the United States can conceivably justify an attack on any individual or group with some plausible link to al Qaeda. Washington would like to disrupt any potentially powerful militant network, but it risks turning relatively harmless local jihadist groups into stronger organizations with eager new recruits. If al Qaeda is indeed becoming a vast collective of local and regional insurgents, the United States should let those directly involved in the conflicts determine the outcome, keep itself out, provide resources only to offset funds provided to radical factions, and concentrate on protecting the homeland.

Following 9/11, the U.S. war on terrorism was framed in the congressional authorization to use force as a response to “those nations, organizations, or persons” responsible for the attacks. The name “al Qaeda,” which does not appear in the authorization, has since become an ill-defined shorthand, loosely employed by terrorist leaders, counterterrorism officials, and Western pundits alike to describe a shifting movement. The vagueness of the U.S. terminology at the time was partly deliberate: the authorization was worded to sidestep the long-standing problem of terrorist groups’ changing their names to evade U.S. sanctions. But Washington now finds itself in a permanent battle with an amorphous and geographically dispersed foe, one with an increasingly marginal connection to the original 9/11 plotters. In this endless contest, the United States risks multiplying its enemies and heightening their incentives to attack the country.

It is precisely because al Qaeda is a shifting adversary that drones have proved so tempting. Globalization has given terrorists potential worldwide reach, and Washington wants to destroy new elements in these networks before they can plan attacks. U.S. policymakers apparently believe that killing fighters before they target the American homeland beats invading another country in the aftermath of an attack. Al Qaeda–associated operatives have been trying to take advantage of unstable situations in Libya, Mali, Yemen, and, especially, Syria. Using drone strikes may allow Washington to keep jihadists from tipping the balance in sensitive places.

U.S. officials also claim that drone strikes have prevented or preempted numerous specific terrorist attacks that would have resulted in American casualties. These claims are hard to verify, but they are intuitive enough. Consider the Yemen-based al Qaeda in the Arabian Peninsula, the source of several attempted attacks against the United States. In 2009, the effort of a would-be terrorist to ignite a bomb hidden in his underwear on a plane on Christmas Day was connected to al Qaeda in the Arabian Peninsula, as was an October 2010 attempt to blow up bombs hidden in printer cartridges aboard two U.S. cargo planes. The drone campaign in Yemen directly responded to these dangers and has reduced the likelihood of similar dangers manifesting themselves in the future.

But other threats to the U.S. homeland have actually been sparked by outrage over the drone campaign. Faisal Shahzad, a naturalized U.S. citizen, tried to bomb Times Square in May 2010 by loading a car with explosives. A married financial analyst, Shahzad was an unlikely terrorist. When he pleaded guilty, however, he cited his anger about U.S. policies toward Muslim countries, especially drone strikes in his native Pakistan.

Indeed, the situation in Pakistan demonstrates that drone attacks exact a clear price in growing animus toward the United States. According to the Pew Global Attitudes Project, only 17 percent of Pakistani respondents to a 2012 poll approved of American drone strikes against the leaders of extremist groups, even if they were jointly conducted with the government of Pakistan. Pakistanis aren’t the only disapproving ones: the vast majority of people polled internationally in 2012 indicated strong opposition to the U.S. drone campaign. The opposition was strongest in Muslim-majority countries, including traditional U.S. allies, such as Turkey (81 percent against), Jordan (85 percent against), and Egypt (89 percent against).

Europeans are almost as unhappy: of those polled in a 2012 Pew survey, 51 percent of Poles, 59 percent of Germans, 63 percent of French, 76 percent of Spanish, and a full 90 percent of Greeks noted their disapproval of U.S. drone strikes. The only publics that even approach the positive attitudes of the United States -- where 70 percent of respondents to a recent New York Times poll approved of drones and 20 percent disapproved -- are in India and the United Kingdom, where public opinion is more or less evenly divided. Washington insiders commonly contend that these popular attitudes don’t matter, since government officials in all these countries privately envy American capabilities. But no counterterrorism strategy can succeed over time without public support.

That is because a crucial element in the success of U.S. counterterrorism has been close collaboration with allies on issues of terrorist financing, the extradition of terrorist suspects, and, most important, the sharing of vital intelligence. Obama ran for office in 2008 on the promise that he would restore the United States’ reputation abroad. But his administration’s unilateralism and lack of transparency on targeted killings are undermining the connections that were painstakingly built over the past decade, particularly with Pakistan and Yemen. This decreases the likelihood that allies will cooperate with Washington and increases the chances of terrorist attacks against Americans.

Of course, if drones actually stop another major attack along the lines of 9/11, they might be worth all the international opprobrium. But for the moment, the only sure thing Washington is doing is driving down international support for the United States and alienating local populations. All this in pursuit of preventing what is almost impossible to stop: a small cell of determined jihadists trying to carry out a minor attack on U.S. soil. That much was made clear by the tragic Boston Marathon bombings in April.

The long-term effect of drone strikes may be that the al Qaeda threat continues to metastasize. An alphabet soup of groups with long-standing local grievances now claim some connection to al Qaeda, including al Qaeda in the Arabian Peninsula, al Qaeda in the Islamic Maghreb, al Qaeda in Iraq, al Shabab (in Somalia), and Boko Haram (in Nigeria). This diversification should come as no surprise. The spread of terrorist groups has historically resulted from campaigns of decapitation and repression. Russia’s assassinations of Chechen leaders between 2002 and 2006, for example, changed the conflict in Chechnya from a separatist insurgency to a broader radical movement in the Caucasus. The Russians killed virtually every major Chechen leader, pummeled Grozny to rubble, and brought Chechnya firmly under Russian control. In that sense, the campaign worked. But violence spread to the nearby regions of Dagestan, Ingushetia, and North Ossetia. Those who argue that the United States should stay the course with drones tend to be the same people who warn that the al Qaeda threat is spreading throughout the Middle East and North Africa. They need to consider whether drone strikes are contributing to this dynamic.

For the moment, there is no conclusive evidence that can prove whether drone strikes create more enemies than they kill. Some academics, including the Pakistan scholar C. Christine Fair and Christopher Swift, who has studied Yemen, argue that no widespread blowback against the United States can yet be detected. They argue that many locals grudgingly support drones and recognize their utility in beating back al Qaeda. Others, however, including the Yemen scholar Gregory Johnsen, warn of a simmering resentment that is driving recruits to al Qaeda. Much of the evidence is highly contested, and the sample sizes used tend to be small and biased toward local officials and educated professionals, who are the easiest to interview but the least likely to become terrorists.

In short, the picture is mixed: drones are killing operatives who aspire to attack the United States today or tomorrow. But they are also increasing the likelihood of attacks over the long term, by embittering locals and cultivating a desire for vengeance.

HOMELAND INSECURITY

Despite the end of the wars in Iraq and Afghanistan, Washington still wants to take the fight to the enemy -- it just wants to do so on the cheap. This makes drones and special operations forces the preferred instruments of U.S. hard power for the moment. Protecting Americans from terrorism may require early action, even preemption, and early action means striking before knowing for certain that a threat is imminent.

Given the shocking nature of terrorist attacks, U.S. counterterrorism policy depends not just on objective measures of effectiveness but also on public opinion. And the American public demands zero risk, especially of a terrorist attack at home. In this sense, drone strikes offer the ideal, poll-tested counterterrorism policy: cheap, apparently effective, and far away.

At first glance, the U.S. government is coming close to meeting that demand: by virtually every quantifiable measure, Americans today are remarkably safe. In the decade following 9/11, the number of people who died in terrorist attacks in the United States plummeted to the lowest since such statistics began to be collected in 1970. The drop owes to both increased public vigilance and heightened defenses at home, but also to U.S. counterterrorism policy abroad, including targeted drone attacks. It is impossible to determine exactly what contribution drones have made to the outcome, but senior U.S. officials have every reason to believe that what they are doing is working.

The near-miss terrorist attacks of the last several years, however, have had widespread effects even in failure. In May 2010, a CNN poll indicated that American fears of a terrorist attack had returned to 2002 levels. Fifty-five percent of those questioned said that an act of terrorism on U.S. soil was likely in the next few weeks, a 21 percent surge from August 2009. That effect has persisted: a 2011 Pew poll indicated that 61 percent of Americans felt that the ability of terrorists to launch another major attack on U.S. soil was the same or greater than in 2001. And a Pew poll in the wake of the Boston bombings showed that 75 percent of Americans now believe that occasional acts of terrorism will persist on U.S. soil, up from 64 percent last year.

In this environment, it is understandable that Americans and the politicians they elect are drawn to drone strikes. But as with the fight against al Qaeda and the conservation of enemies, drones are undermining U.S. strategic goals as much as they are advancing them. For starters, devoting a large percentage of U.S. military and intelligence resources to the drone campaign carries an opportunity cost. The U.S. Air Force trained 350 drone pilots in 2011, compared with only 250 conventional fighter and bomber pilots trained that year. There are 16 drone operating and training sites across the United States, and a 17th is being planned. There are also 12 U.S. drone bases stationed abroad, often in politically sensitive areas. In an era of austerity, spending more time and money on drones means spending less on other capabilities -- and drones are not well suited for certain emerging threats.

Very easy to shoot down, drones require clear airspace in which to operate and would be nearly useless against enemies such as Iran or North Korea. They also rely on cyber-connections that are increasingly vulnerable. Take into account their high crash rates and extensive maintenance requirements, and drones start to look not much more cost effective than conventional aircraft.

Another main problem with Washington’s overreliance on drones is that it destroys valuable evidence that could make U.S. counterterrorism smarter and more effective. Whenever the United States kills a suspected terrorist, it loses the chance to find out what he was planning, how, and with whom -- or whether he was even a terrorist to begin with. Drone attacks eliminate the possibility of arresting and interrogating those whom they target, precluding one of the most effective means of undermining a terrorist group.

It is worth noting that the most dramatic recent decapitation of a terrorist organization -- the killing of bin Laden -- was performed by humans, not drones. As a result, the most important outcome of the operation was not the death of bin Laden himself but the treasure trove of intelligence it yielded. Drones do not capture hard drives, organizational charts, strategic plans, or secret correspondence, and their tactical effectiveness is entirely dependent on the caliber of human intelligence on the ground. And if the unpopularity of drones makes it harder to persuade locals to work with U.S. intelligence services, then Washington will have less access to the kind of intelligence it needs for effective targeting. Yes, killing would-be terrorists saves American lives. But so does interrogating them, and drone strikes make that impossible.

Finally, the drone campaign presents a fundamental challenge to U.S. national security law, as evidenced by the controversial killing of four American citizens in attacks in Yemen and Pakistan. The president’s authority to protect the United States does not supersede an individual’s constitutional protections. All American citizens have a right to due process, and it is particularly worrisome that a secret review of evidence by the U.S. Department of Justice has been deemed adequate to the purpose. The president has gotten personally involved in putting together kill lists that can include Americans -- a situation that is not only legally dubious but also strategically unwise.

PASS THE REMOTE

The sometimes contradictory demands of the American people -- perfect security at home without burdensome military engagements abroad -- have fueled the technology-driven, tactical approach of drone warfare. But it is never wise to let either gadgets or fear determine strategy.

There is nothing inherently wrong with replacing human pilots with remote-control operators or substituting highly selective aircraft for standoff missiles (which are launched from a great distance) and unguided bombs. Fewer innocent civilians may be killed as a result. The problem is that the guidelines for how Washington uses drones have fallen well behind the ease with which the United States relies on them, allowing short-term advantages to overshadow long-term risks.

Drone strikes must be legally justified, transparent, and rare. Washington needs to better establish and follow a publicly explained legal and moral framework for the use of drones, making sure that they are part of a long-term political strategy that undermines the enemies of the United States. With the boundaries for drone strikes in Pakistan, Somalia, and Yemen still unclear, the United States risks encouraging competitors such as China, Iran, and Russia to label their own enemies as terrorists and go after them across borders. If that happens -- if counterterrorism by drone strikes ends up leading to globally destabilizing interstate wars -- then al Qaeda will be the least of the United States’ worries.