All we had in Vietnam were advisors for several years until they started being killed and JFK did the dreaded mission creep.There's no diference between combat troops and non-combat troops.
But there is a difference between a combat role and a non-combat role. Perhaps that is why the announcement was written to say this:
""additional U.S. military personnel in a non-combat role to train, advise, and assist Iraqi Security Forces, including Kurdish forces" against ISIS."
The Kurds and Iraqis are in the combat role.
Yeah, here's the "training and advice:"
Got out on patrol with a unit, kill a few from the other side then say, "that's how you do it." These advisers are fighting alongside the ISF and Kurds and in many cases are directing their actions. Calling it a "non-combat role" is just political cover and always has been.