President Barack Obama has vowed to "degrade and ultimately destroy" Islamic State, or ISIS. That will be difficult without boots on the ground, and if those boots are American, it means a major war in Iraq and Syria. Furthermore, even if we invade and destroy ISIS, we will withdraw in a few years, and something like ISIS will probably just come back.
What we need is an ally to put boots on the ground against ISIS, who can also act to stabilize the region after ISIS is dispersed. Turkey is out -- even its feint toward limited intervention in Syria generated massive internal dissent. Saudi Arabia doesn't have the capability. There's only one potential strategic partner left: Iran.