U.S. troops could be in Syria indefinitely. Here's why

Turkey's military appeared ready on Friday to invade a Kurdish area of Syria and attack a force who, backed by the U.S., helped liberate Raqqa from the Islamic State. While the U.S. wants to convert them into a stabilization force, Turkey's president says they are a grave threat. Nick Schifrin talks with former Pentagon official Andrew Exum and Mona Yacoubian of the U.S. Institute of Peace.

(Source: PBS NewsHour, https://www.youtube.com/watch?v=EjfStxF2lCs)