It is a truism to say there is no military solution to ISIS. Any strategy must, of course, be comprehensive. It must squeeze ISIS’ finances. It requires an inclusive government in Baghdad that shares power and wealth with Iraqi Sunnis, rather than pushing them toward ISIS. It requires an end to the conflict in Syria, and a political transition there, because the regime of President Bashar al-Assad will never be a reliable partner against ISIS; in fact, it has abetted the rise of ISIS, just as it facilitated the terrorism of ISIS’ predecessor, Al Qaeda in Iraq. A strategy to counter ISIS also requires a regional approach to mobilize America’s partners in a coordinated, multilateral effort.

But ultimately, ISIS is a military force, and it must be confronted militarily. Mr. Obama has begun to take military actions against ISIS in Iraq, but they have been tactical and reactive half-measures. Continuing to confront ISIS in Iraq, but not in Syria, would be fighting with one hand tied behind our back. We need a military plan to defeat ISIS, wherever it is.

Such a plan would seek to strengthen partners who are already resisting ISIS: the Kurdish pesh merga, Sunni tribes, moderate forces in Syria, and effective units of Iraq’s security forces. Our partners are the boots on the ground, and the United States should provide them directly with arms, intelligence and other military assistance. This does not, however, mean supporting Iranian military forces, whose presence only exacerbates sectarian tensions that empower ISIS.