Yet another article that glosses over the fact that the civil war in Syria is also a Russian/US conflict and could spiral into a full on proxy war in the same vein as Korea and Vietnam.
Russia is supplying military assistance to the government of Syria, while the U.S. (and other NATO countries) are supplying assistance to moderate Syrian rebel groups (but not ISIS). This breaks it down clearly:
http://mobile.nytimes.com/2015/10/01/world/middleeast/the-sy...
This just happened recently:
http://mobile.nytimes.com/2015/11/25/world/europe/turkey-syr...
Russia has repeatedly warned the US to not interfere directly in Syria (you might have seen this):
http://www.nytimes.com/2013/09/12/opinion/putin-plea-for-cau...
This is all interesting considering the Republicans are already talking about increasing the US presence in Syria (for the purposes of defeating ISIS).
http://edition.cnn.com/2015/11/16/politics/republican-isis-2...
Statistics are nice but the model is too simple and doesn't account for the complexities of geopolitics.