In his speech to the American people tonight, President Obama aims to build support for a protracted military campaign against the Islamic State in Iraq and Syria (ISIS). It doesn't have to be a hard sell. A majority of Americans support a military response—though not U.S. troops on the ground. Very few are content with allowing ISIS to spread its influence with impunity, especially after the brutal killing of the American journalists James Foley and Steven Sotloff. But, writes Christopher Preble, a full-scale ground war isn't necessary. The president should focus upon degrading ISIS's capabilities, and resist the calls to launch the U.S. military on yet another quixotic nation-building crusade in the Middle East.