What Are US Troops Guarding (And Dying For) In Syria?

Writes Daniel McAdams:

The killing of two US National Guard troops and one interpreter – and wounding of other US personnel – in Syria over the weekend forces once again the question: WHY are US troops STILL in Syria? What is their mission? How is it in the US national interest for them to be there? And WHY are we building yet ANOTHER base in Syria?