PETER FEAVER is Professor of Political Science and Public Policy at Duke University. HAL BRANDS is Henry A. Kissinger Distinguished Professor of Global Affairs at Johns Hopkins University’s School of Advanced International Studies and a Senior Fellow at the Center for Strategic and Budgetary Assessments.

The United States will soon reach a crossroads in its struggle against terrorism. The international coalition fighting the Islamic State (also known as ISIS) has driven the group out of much of the territory it once held and, sooner or later, will militarily defeat it by destroying [1] its core in Iraq and Syria. But military victory over ISIS will not end the global war on terrorism that the United States has waged since 9/11. Some of ISIS’ provinces [2] may outlive its core. Remnants of the caliphate may morph [3] into an insurgency. Al Qaeda and its affiliates will still pose a threat. Moreover, the conditions that breed jihadist organizations will likely persist across the greater Middle East. So the United States must decide what strategy to pursue in the next stage of the war on terrorism.

On the campaign trail, Donald Trump called for sweeping changes in U.S. counterterrorism strategy, promising [4] to “defeat the ideology of radical Islamic terrorism.” As president, he faces a broad range of choices. At one extreme, Washington could abandon its military commitments in the greater Middle East on the assumption that it is U.S. interference that provokes terrorism in the first place. At the other, it could adopt a heavy-footprint surge strategy that would involve using overwhelming military force to destroy globally capable terrorist organizations and attempt to politically transform the societies that produce them. In between lie two options: one, a light-footprint approach akin to that taken by the Obama administration before ISIS’ rise; the other, a more robust approach closer to Washington’s response to ISIS since late 2014. 

None of these four strategies is ideal. The extreme options—disengagement and surge—promise to dramatically reduce the threat. But both would likely fail in costly ways, and both are politically untenable today. The middle choices pose less risk and are more politically palatable. But they also promise far less and would likely leave the United States stuck in a protracted conflict. 

Trump must therefore