from Al Jazeera: Pentagon says the additional forces have been in Syria for ‘a while’, before fall of President Bashar al-Assad, though they were not publicly disclosed. How long? Months “at a minimum”. Why? Probably three reasons: 1. Deter Turkish attacks on US-allied Kurds. 2. Ensure the containment of 10,000 ISIS fighters (and ~30,000 kin and suspects). 3. Deter the possible advance of HTS on the US and Kurdish held Syrian oil fields. Leverage.