Well, I am being a bit snarky. U.S. Special Forces have been in Syria since 2014 as part of Operation Inherent Resolve. But the recent uptick in conventional forces there is significant — and under-reported in my opinion. Here is my round-up of the units now in Syria and their probable missions in the fight against Daesh/ISIS.
ICYMI, The U.S. Just Invaded Syria
The Pen and The Sword 