After ISIS: U.S. Political-Military Strategy in the Global War on Terror
The United States is approaching a strategic pivot in its struggle against jihadist terror groups. It appears increasingly likely that ISIS will be militarily defeated, even if the precise timing remains uncertain. The core of ISIS’s self-declared caliphate in Iraq and Syria will be destroyed; the group will no longer exert control over significant territory or population in those countries. ISIS will go down fighting, of course, and do enormous amounts of harm in its death throes. Yet given the formidable international forces—anchored by the U.S. military—arrayed against it, and the organization’s increasingly desperate military situation, it seems highly probable that ISIS’s days are numbered.
Defeating ISIS militarily, however, will not bring decisive victory in America’s broader conflict with jihadist terrorism. The United States has been waging that struggle for decades; it has been fighting the post-9/11 Global War on Terror (GWOT) for more than 15 years. This conflict will persist even after ISIS has passed from the scene. Some of ISIS’s “provinces” in countries such as Libya or Egypt may endure; the threat posed by al Qaeda and its various affiliate organizations will remain. More broadly, so long as the root causes of jihadist ideology persist throughout much of the greater Middle East and beyond, so too will the threat itself. Indeed, the fact that the United States has now confronted multiple iterations of the GWOT over the past 15 years—first against core al Qaeda (AQ), then against the AQ affiliates, and now against ISIS—warns against expecting lasting victory in that conflict anytime soon. The end of intense hostilities against ISIS may merely mark the beginning of a new stage in the debate on what strategy will best protect America in the age of terror.
So, what political-military strategy should America pick? The range of plausible choices is broad and encompasses four principal options. At one end of the spectrum, Washington could withdraw its military forces from the greater Middle East in hopes of averting the ideological blowback that is sometimes alleged to cause or at least exacerbate the terrorist threat. At the other end of the spectrum, the United States could conduct a “GWOT surge”—a heavy footprint approach comparable to the political-military approach seen in Iraq and Afghanistan at the height of the post-9/11 conflicts there. Under this strategy, the United States would conduct decisive military operations against any ISIS- or al Qaeda-like organizations that might remain or emerge following ISIS’s military defeat, as well as intensive efforts to go to the source of the problem by fostering political liberalization and effective governance in the societies from which terrorist threats arise.
In between these extremes are two more moderate strategies. One is a “light-footprint” approach similar to the Obama administration’s strategy between 2011 and 2014, featuring a reliance on drone strikes and other long-reach attacks to hold the most dangerous terrorist organizations at bay. The other is a more intensive, medium-footprint approach that resembles—and perhaps somewhat exceeds—the culmination of the Obama administration’s post-2014 efforts to defeat ISIS. This strategy combines aggressive air campaigns, special operations forces raids, advise-and-assist operations, and even deployment of modest numbers of ground combat forces as part of a continuing effort not just to contain the most dangerous terror groups, but to roll them back and defeat them militarily.
Each of these strategies rests on an internal logic—a theory of the case—about what causes jihadist terrorism, how much the United States can reasonably expect to accomplish in countering that threat, and what level of cost and risk the country ought to accept along the way. Unpacking the logic of these various approaches, and more systematically assessing their strengths and weaknesses, is essential to charting America’s strategic course in the years ahead.
Unfortunately, there is no clearly dominant GWOT strategy. In theory, the options at the far ends of the spectrum—disengagement on the one hand and GWOT surge on the other—could markedly reduce the terrorist danger. In practice, however, both strategies are unlikely to deliver on their ambitious promises. Disengagement is unlikely to ease the sources of jihadist anger at the United States sufficiently to offset the security vulnerabilities and other geopolitical costs that military withdrawal from the Middle East would cause. GWOT surge, for its part, will probably not actually bring about military victory and political transformation of the greater Middle East—at least at a cost that most Americans would find acceptable. Both strategies are thus likely to fail in very damaging ways—aside from being politically infeasible in the current domestic climate. The two moderate options, by contrast, are more acceptable politically and pose less risk of catastrophic failure. But they entail potent drawbacks and limitations of their own, and they are likely—even in the best-case scenarios—to leave the United States in a protracted, ongoing conflict with jihadist groups for many years to come.
Ultimately, choosing a strategy involves selecting the least-bad option. And the least-bad of America’s strategic options today is a medium-footprint option building on the counter-ISIS campaign that has been waged since 2014. If employed consistently and aggressively, this option holds some promise of rolling back powerful terrorist organizations militarily and thus keeping the threat at a manageable level, without incurring unacceptable resource costs or military risks in the process. But even this approach is rife with dilemmas, and there should be no illusions that it will deliver conclusive victory in a conflict that may very well endure for many years to come.
 The Islamic State is variously rendered as ISIS, ISIL, or DAESH (the Arabic acronym). This study will refer to it as ISIS (Islamic State of Iraq and Syria) but will maintain the rubrics used by various quoted sources in the citations.
 This article is an expanded version of an argument the authors make in Hal Brands and Peter Feaver, “Trump and Terrorism: U.S. Strategy after ISIS,” Foreign Affairs 96, no. 2, March/April 2017. Here, we focus primarily on the political-military dimensions of American strategy. These dimensions do not constitute the entirety of American strategy, of course, but they constitute one essential dimension of that strategy and are thus deserving of intensive analysis. Moreover, the political-military aspects of American strategy are actually more susceptible to open-source analysis than are issues such as the intelligence or even homeland security dimensions of counterterrorism.
 We say “culmination” to make clear that Obama’s counter-ISIS strategy intensified over time; the low end of the medium-footprint approach discussed in this article resembles not the relatively anemic approach taken by the administration in August and September 2014, but rather the intensified approach being pursued from late 2015 onward.