"The risk for Moscow is that Syria becomes its second Afghanistan or, more accurately, a Russian Vietnam. The Vietnam analogy is better than the Afghan one because the Soviet Union suddenly and fully invaded Afghanistan, as opposed to the US in Vietnam which escalated and dithered until it found itself in a full-blown war.
The amount of power necessary to reorder Syria is staggering. The price tag on the refugee crisis alone can’t yet be calculated. To bring regime power back to all of Syria’s provinces would require a commitment of troops and power that could well cripple Russian efforts to carry out any of its basic defense needs, including holding Ukraine and keeping a lid on Chechnya.
Even to carve out an Assad enclave will be terribly expensive and dangerous. No faction is content with such a slice of the pie: everyone is fighting to the death. To convince the FSA, Jabhat al-Nusra and the Islamic State to leave the Alawite homeland alone will require an open-ended commitment of troops and equipment that Russia can ill-afford.
Worse, if Russian troops are killed in some headline-grabbing attack, Putin may face pressure to either escalate, as he did in Chechnya, or pull out. He can’t manage Syria as he does Ukraine where he holds the leash to the Donbas rebels’ collar."