Just west of a coalition base in northern Syria, Turkish-backed fighters approached US troops until they were dangerously close, pushing them to call in jets and attack helicopters for defense. The encroachment violated an agreement not to threaten US troops, and a formal complaint was sent to the Turkish military after the event had settled. While US service members and equipment were never in direct jeopardy, securing the Coalition forces is a priority as they conduct a deliberate withdrawal.

Source: Yahoo!