From ABC News:
“Working in small teams, the special operations troops also provide explosive ordnance disposal assistance, and facilitate the communications and coordination needed for coalition airstrikes that have helped SDF fighters push ISIS out of long-held strongholds in northern and eastern Syria.
The American forces are supposed to do their work at the headquarters level, remaining behind the front lines. But given the fluid nature of the battlefield in Syria and the less structured command structure in the SDF, the American advisers can find themselves in a combat environment where they have to defend themselves if they come under attack.
The U.S. military program to assist the SDF began in early 2016 with a force of 50 special operations forces to gauge the group’s fighting capabilities and reliability as a local partner in the fight against ISIS.
Based on the success of that effort, President Barack Obama ramped up the operation in April by authorizing 250 more special operations forces to go to Syria.”