You might want to bookmark this article as a handy reference for the particulars of all the participants in Syria. From Jack Parry at lewrockwell.com:
Okay, folks, you won’t be able to know who’s who in this Syrian War without a program! So, without further ado, enjoy!
First off, there’s several different factions over there and not all of them willingly get along. Syria has: Shi’ite Muslims, Sunni Muslims, Syrian Orthodox Christians, a small number of Catholics, Kurds, Alawite Muslims, Druze, Yazidis, and the current imported Wahhabis called ISIS and al-Nusra. The surrounding nations do not all appreciate this mix of diversity. See, Assad is an Alawite Muslim, which is how he could walk the tightrope between these various factions, since the Alawite are a tiny minority themselves.
So…neighboring Iran is Shi’ite and controls the paramilitary militias of Hezbollah and the Revolutionary Guard who have fought in Iraq and Syria. They back Assad and hate ISIS. Iran does not want to see another Sunni nation pop up on its border, which they fear will happen if we topple Assad. The United States always backs Sunni Muslims and so this fear is not without foundation. The animosity between Sunni and Shi’ite is well known. So, Iran can be counted on to supply Hezbollah and Revolutionary Guard martyr brigades to any war in Syria that a would-be Sunni government is seeking to win.
Then we have neighboring Turkey, who hates Assad and ISIS, but also hates the Kurds who are one of our anti-ISIS allies. Turkey would like nothing more than to see Assad toppled and ISIS gone, but after that, the Kurds better not try to create an autonomous republic which is one of their stated goals. In fact, Turkey is engaged in a guerilla war against Kurdish separatists who hit Turkish security forces in Turkey and then run across the border into Syria to escape. The Kurdish militias themselves are mostly quasi-Marxist pseudo-socialists, but all of them are agreed that they will create an autonomous Kurdish republic once this is over. Which the Turks, our NATO ally, will not accept.
To continue reading: Syrian Scorecard