This shit is complicated as hell, now a Turkey, Iran and Russia are supposed to be working together, but all three have clients and support people on both sides. Turkey says it fights ISIS, gets attacked by them, but allows them refuge, hospitals and to cross the border if they are attacking Kurds. Russia supports Assad, but also helps Turkey and the Kurds. The US helps the Kurds (now abandoned) and is in a NATO alliance with Turkey, who helps the enemies of the US, etc. The Gulf States support the same rebels that Turkey does, hate Iran. Also Turkey helps launder Iranian oil and gives them gold, under the nose of US sanctions.

So everyone is involved, on every side it seems.