We’re at a dicey point in Syria. When Al Qaeda-affiliated rebels made gains against the Assad government in Summer 2015, the Russkies greatly increased their support for Assad in September 2015. The Obama administration predicted that this would turn into an Afghanistan-like “quagmire” for the Russkies. It still may, but that isn’t what has been happening recently. Instead, the Russian-backed offensive by the Assad government has cut the major supply routes from Turkey to the northern anti-Assad groups. It may go on to crush its opponents in Western Syria and bring that part of the war to an end.
Alternatively, other powers like Turkey and Saudi Arabia could pile on so that the effort to unseat Assad continues. Intervention by Saudi Arabia and Turkey would not be just for spite. The Sunni-Shi’a civil war within Islam provides the context for this decision. To see Assad survive in control of western Syria would mean that a client-state of Iran had tightened its grip. The Wall Street Journal‘s Yarolslav Trofimov reports that such an outcome would be regarded as a “catastrophe” in the minds of Turkish and Saudi leaders. “Can we accept Russia and the Iranians calling the tune in the region?” asked one Turkish diplomat. Many Sunni observers appear to believe that Russian intervention will trigger greater intervention by the Sunni powers.
How? For one thing, the primary supply line into Syria appears to run through Turkey. If that line is cut, will the Saudis try to open (or expand an existing one) through Jordan? For another thing, the key element in the Russian effort has been air power. Would Turkey or Saudi Arabia commit their own air forces against the Russians? Well Turkey did in November 2015, when it shot down a Russian strike jet that had invaded Turkish airspace on a bombing run. The Turks have been quaking in their boots ever since.
There are many questions, great and small.
The ground-based air-defense systems (anti-aircraft missiles) of Turkey and Saudi Arabia come from the United States. Would the US sign-off on transferring these to Syrian opponents of the Assad government?
Even if the Russkies were to back away, would Iran and Iraq? They are front-line states in the Muslim civil war. The outcome in Syria is just as important to them as it is to Turkey and Saudi Arabia.
Would Turkey (and possibly Saudi Arabia) launch a conventional ground-force intervention? The Turkish military has been under attack by the Erdogan government. Their price for agreeing might be high. The Saudis haven’t been in a real war for many decades.
One of the key long-term purposes of both the NATO and Warsaw Pact alliances was to rein-in the foreign policy independence of the client states of the United States and the Soviet Union. Has the ending of the Cold War unleashed the client states to do any damn-fool thing that seems to be a good idea at the moment?
The 2003 invasion of Iraq looks worse and worse all the time. If that is possible.
 Yaroslav Trofimov, “Russian Victories Mark Turning Point in Syria,” WSJ, 12 February 2016.
 I suppose you can think of it as “inhumanitarian aid.” However, what is more “humanitarian” in this context: to end the war now or let it drag on along the same awful lines of the last five years?
 In the early days of the Iraq occupation, the Bush II Administration refused to call what was happening an “insurgency,” although it plainly was an insurgency. Now, the Obama administration seems reluctant to recognize that this civil war has created difficult problems for their Middle Eastern policy. Back in the day, the historian Henry Adams had great fun showing how the administration of Thomas Jefferson had been driven to adopt many of the policies of the previous John Adams administration—which Jefferson had bitterly criticized during the campaign. HA! Is joke.
 See John Lewis Gaddis, The Long Peace: Inquiries into the History of the Cold War (1987).