Without an inchoate caliphate, ISIS becomes another bunch of terrorists roaming in the area, competing with several others.ISIS can be defeated, and quite readily. It set itself up as an easier target than other terrorist groups when it defined itself as seeking to found a state, governed in line with its particular interpretation of Islam.
If America doesn't have the stomach for such an open-ended commitment -- and honestly, it's hard to imagine a successful candidacy for the White House in 2016 built around the theme, "Let's Re-invade Iraq" -- the options get much more limited. But there are three things that would make a difference.
One of the main prerequisites to defeating ISIS in Iraq is to determine the political future of Sunni Iraqis. The Sunnis are not prepared to make all the needed sacrifices only to benefit the Shiite government in Baghdad, which they reject and despise even more than ISIS. The Obama administration must begin, concurrently with the fight against ISIS, to negotiate the future status of the Sunni Iraqis.
The U.S. has the most powerful military in the history of the world, but it should not be utilized as a political tool or for retribution. The government and its leaders must do their best to make the right decisions, to be truthful with the American people, and to provide all the necessary support needed to fulfill the military's mission. Unfortunately, this has not always been the case.
There are strong arguments making the case for the persistence (and indeed the intensification) of U.S. airstrikes against ISIS targets. But equally there are strong arguments, less frequently heard perhaps, for why the United States should not continue, and should certainly not intensify, those airstrikes.
At the level of global affairs, there hasn't been anything like ISIS since Genghis Khan left immense piles of skulls outside conquered cities and dared the world to gang up against his Mongol horde. Genghis Khan didn't negotiate. The only word in his diplomatic vocabulary was capitulation. So too with ISIS and its dream of a caliphate of the oppressed.
Perhaps with international efforts, ISIS can be contained, weakened and driven back to its stronghold in Syria. But it isn't expected to die an easy death. Even so, its crimes against humanity demand all efforts. The Khmer Rouge, left to their own devices, murdered nearly a quarter of its own population.