This is something I have been warning about for the last few days. Iranian-backed militia have been amassing near a U.S. training base in Syria (what legal justification does the U.S. have to be in Syria anyway?)
The U.S. led coalition just struck them directly.
Regardless of your thoughts on Assad and Iran, the Assad military and its associated forces were found to be the most heavily engaged entities fighting ISIS last year. Meaning that if you want to defeat ISIS, attacking Assad's forces makes no sense at all.
There have also been reports that these troops are backed by the Russian air force. This is a recipe for disaster.
For sources:
http://www.reuters.com/article/us-mideast-crisis-syria-usa-idUSKBN18X2JP
http://theantimedia.org/happens-overthrows-syrian-government/