There is an intellectually respectable case to be made that the United States should do nothing, or next to nothing, to destroy the terrorist force known as ISIS. It goes something like this -- despite its beheadings and its threats, ISIS should be seen as a regional force more intent on capturing territory in the Mideast than trying to attack a superpower an ocean away.
Any strategy to defeat ISIS that relies largely on air power can certainly make things harder for ISIS fighters, but it takes ground troops to dislodge occupiers from conquered territory. U.S. ground troops might be the only force capable of truly defeating ISIS, but their introduction, especially in Syria, would be a throw of the dice against utterly unpredictable odds. The Mideast -– this argument goes -- is in the midst of an historic upheaval that should be permitted to run its course, not because things will turn out well but because it's unlikely American military force can make them turn out better.
I don't buy this whole argument, but I sense that President Obama does, and would have preferred to take no action against ISIS beyond some air strikes in Iraq. But he felt his hand was forced by the public's outrage and alarm over those videotaped beheadings. So he came up with a strategy for ISIS's eventual defeat, which is designed not to succeed so much as to fail slowly in a mission he doubts should even be undertaken.