Can the U.S. defeat ISIS without removing Assad?

So what happens if the United States does change course? There are strategic benefits to removing Assad from power, of course, but there is no end to the political and military complications either. While the American-led coalition has targeted Islamic State forces and installations in Syria from the sky, they’ve done so without having to confront Assad’s considerable air forces. If the United States throws the Syrian regime into its crosshairs, the mission in Syria will likely get considerably thornier.

Then, of course, there is the matter of Russia and Iran, who may be theoretically on board with the effort to stop ISIS, but who have sought to arm and keep afloat the Assad regime throughout the three-and-a-half years of the Syrian civil war and have blocked every international effort to oust him from office. Both countries have given no sign of relenting on that front.

Meanwhile, degrading ISIS remains as difficult as ever. On Thursday, an audio tape was released of what appears to be Islamic State leader Abu Bakr al-Baghdadi taunting the United States just days after he was reported injured in an airstrike. Add to this confounding mix a statement on Thursday by House Armed Services Committee Chair Buck McKeon that directly challenged the president’s pledge for “no boots on the ground” and threatened to veto an Authorization for the Use of Military Force in a congressional hearing.

So my fundamental question is: how can you successfully execute the mission you’ve been given—to ‘degrade and ultimately destroy’ ISIL—when some of your best options are taken off the table? Mr. Secretary, both of your predecessors, Bob Gates and Leon Panetta, have stated that we need boots on the ground if there’s to be any hope of success in the strategy.