Executive Summary

In 2011, the United States withdrew its last combat troops from Iraq. Yet fewer than three years later, the Obama administration, which viewed the withdrawal as a correction of one of the greatest foreign policy failures of the modern era, initiated a counterterrorism war against ISIS in Iraq. The administration then extended the war to Syria. In doing so, it presented a number of justifications for war, among them preventive war logic, which is the view that war now is preferable to other options as a way of preventing a future conflict in which a rival would pose a greater threat due to a growth in its capabilities.

The counter-ISIS war accomplished much good. It destroyed ISIS's territorial caliphate that, at one point, ruled over almost 8 million people and encompassed an area about the size of Britain. Nestled in the heart of the Middle East, it was the launchpad from which ISIS carried out attacks in Europe and elsewhere.

Yet the war poses significant questions for American counterterrorism strategy. What rationales were used to justify the use of American military power? Did preventive war logic play a role in the decision? Did ISIS directly threaten the United States? Has the counter-ISIS war made the United States safer?

Horror at ISIS's atrocities and terror has helped sideline these questions. This report examines the counter-ISIS war as a historical case study to resurface them. It also seeks to draw out their lessons for use in efforts to end America’s endless wars and to develop sustainable counterterrorism strategies. Its findings include:

• The Obama administration publicly invoked preventive war logic as part of its justification for the counter-ISIS war, and in particular, its extension into Syria. The administration expressed fear that if left unchecked, ISIS would grow to pose a threat to the American homeland and cited that fear as the basis for airstrikes.
• While preventive war logic played an important role, regional security, protection of Americans abroad, and humanitarian concerns and genocide prevention rationales drove the decision to initiate the war. These rationales were given more importance earlier in the decision-making process’s public justifications than preventive war logic. They also played a more direct role in the decision to view ISIS as posing a threat requiring action in June 2014 and in the decision to initiate limited airstrikes in August 2014.
• As the United States confronted ISIS's brutal methods and its threat outside the homeland, decision makers increasingly perceived ISIS as fundamentally incompatible with American values. The emergent discourse of “common threat” rooted in these other rationales and an inferred eventual threat to the United States helped push forward preventive war logic. In turn, the uncertainty that comes with projecting future threats central to preventive war logic encouraged a shift to such values-matching reasoning, creating a feedback loop.
• The importance of different rationales shifted over time, often in reaction to events, warning against viewing promises to end endless war or exercise restraint as the expression of stable preferences. Even the most restraint-oriented decision makers will be tempted to escalate wars under certain conditions.
• ISIS did not pose a direct threat to the United States that would support a case that the war was preemptive. The administration repeatedly stated that there was no credible evidence of specific and imminent ISIS-directed plots against the homeland. A review of jihadist terrorism-related criminal charges in the United States as well as other indicators suggests that this assessment was correct.
• While ISIS has shown no capability to direct an attack inside the United States, ISIS's virtual coaching of attackers and its threat to aviation standout as deserving of deeper analysis and public debate. These threats, in particular the online “enabled” plotting, could conceivably ground an argument that U.S. action was preemptive. However, they were not at the center of the decision to initiate the war and viewing them as sufficient grounds for preemption raises its own risks.
• ISIS did pose a direct threat to Europe, many Middle Eastern states, and the people of Iraq and Syria. ISIS directed major attacks in Europe, conquered Iraqi and Syrian cities, instituted a system of slavery, kidnapped and murdered Americans, and committed genocide. The group also repeatedly demonstrated its intent and ability to spread and direct violence across the Greater Middle East through support for affiliates.
• The ISIS threat to Europe was preceded by substantial warnings of ISIS's capability to conduct such attacks. This stands in stark contrast to the lack of evidence of ISIS's capability to strike the United States.
• The public adoption of preventive war logic fueled America’s endless wars and poses substantial risks for escalation. This effect is rooted in predictable results of the logic itself and is visible in the counter-ISIS campaign’s aftermath.
  • Justifications shifted from arguments framed by cost-benefit analysis to justifications based in matching American values. Policymakers justified war citing ISIS's incompatibility with world order and its evil nature. The extent of this shift, however, is contested.
  • ISIS's annihilation has proven impossible. Policymakers have over-focused on the group’s capabilities while ignoring the broader political conditions underlying the conflict. This is typical of preventive war strategies, and poses substantial risks of escalating and prolonging war.
  • Preventive war logic loosens the required level of threat for military action and risks overtaxing American power while also creating conditions for future wars.
• Calls for withdrawals from America’s wars are insufficient on their own to end endless war. As long as the United States maintains interests in regions facing resilient jihadist insurgencies, it will be prone to re-escalation. The Obama administration did not intend to return to waging war in Iraq. That it did so, and initially justified its return on limited aims, suggests that a politics of embracing withdrawal is insufficient.
• Trump’s withdrawal from northeastern Syria is not an end to endless war and risks setting the stage for a snapback of American military power.
  • U.S. forces will remain in the al-Tanf area of Syria with a counter-ISIS mission, but they will also be in effect aiding American competition with Iran and Russia.
  • U.S. forces will also likely remain in eastern Syria, purportedly to protect access to oil, potentially resulting in no net decrease in troop presence.
  • The Defense Department is seeking ways to continue airstrikes and surveillance.
  • Trump has committed the United States to monitoring the conflict so as to be able to re-intervene if ISIS gains power to prevent another situation like 2014, reinscribing the preventive war logic that began the counter-ISIS war.
• Calls for withdrawal or an end to endless war must be combined with substantial efforts to change America’s vision of its role in the world, efforts to improve conditions on the ground, and development of non-military policy options to avoid a snapback of war. In the absence of such efforts, advocates of restraint will find themselves putting unwarranted faith in the statements of politicians rather than a full policy program to end America’s wars.