(Sorry, it's another long one — but it had to be.)
The Russians and the Turks are rather upset with each other at the moment, Turkey having shot down a Russian aircraft that was bombing northern Syria. The Islamist State (as I prefer to call it,) most Americans might be surprised to learn, was not at all involved.
Putin and the Russians support Bashar al-Assad, the Allawite leader of Syria. Russia has an ongoing deal with Assad which permits Russia to maintain its only military/naval presence in the Middle East. Turkey under Erdogan is dominated by an authoritarian Sunni Islamist party hostile to Assad and his Allawists, although Erdogan's primary goal in the region is to suppress the Kurds, who have been getting closer to having their own, autonomous state. To defeat the Kurds, Erdogan has made use of Turkmen rebels, who happened to be be concentrating their own efforts on both Assad and the Kurds, and whom the Russians bombed for being anti-Assad. The Kurds, of course, have been the only effective US ally in the region.
Meanwhile, Saudi Arabia and the Gulf States have been restricting most of their bellicosity to Yemen, where they are trying to destroy the Houthi. The Houthi have some degree of support from Iran, Saudi Arabia's chief rival in the region. Iran, its Shi'ite proxy Hezbollah, and Russia are cooperating in support of Assad.
So where does IS come in? Good question. And where does the USofA come in? Better question.
IS offends Western sensibilities in a variety of bloodthirsty ways, so the US is necessarily against it. Inspired by Salafi Islamists from Saudi Arabia, and probably making use
of private Saudi seed money, IS has been endeavoring to create and
maintain a Sunni extremist caliphate in Iraq and Syria. Some of our "allies," though, are far more concerned with Assad and Iran than with IS atrocities. The USofA is providing Saudi Arabia "logistic support" (telling them where to bomb the most civilians?) in Yemen, thereby helping their proxy war against Iran. In Iraq, however, the Iranians are our chief allies in protecting what was supposed to be our puppet regime. In reality, though, it's their puppet regime because we let it be dominated by Shi'ites.,
Turkey, a NATO ally, really has nothing in particular against IS, considering how it is keeping the Kurds from establishing an independent state on Turkey's border. The Turkish border with Syria restricts the IS supply of weapons, war materiel and foreign fighters about as well as a chain link fence obstructs the flow of water. Bear in mind that Turkey is part of NATO, and supposedly opposed to IS, but since it started bombing in northern Syria, its primary targets have been the US allied Kurds.
In brief, since the USofA opposes both Assad and IS, and since others in the region have mixed feelings about which other groups present the greatest threat to their own self-interests and different historically and geopolitically based affinities and animosities, there are too damned many sides, and every new development creates more ambiguity.
It's a ridiculous time for anybody to want to be president, which sheds a little light on the general ridiculousness of foreign policy discussions in the current campaign. If we adopt Hillary's "no-fly zone" idea, who do we enlist to help us and who do we keep out? If we follow Lindsey Graham's prescription and send in ground forces to eradicate the "State" part of IS, it might turn out much more difficult to contend with a stateless enemy.
We're probably leaning on the Turks and the Saudis and the Iranians and the Russians and anybody else who has a real state as hard as we can, but our diplomatic pressure is spread too thin. Don't blame Obama (this time) — at least he's not actively making it worse.