This is coolbert:
Those American advisers in Iraq now in mortal combat with ISIL elements. That first encounter having gone to the advantage of U.S. forces.
"ISIS Attacks American Base In Iraq In First Ever Clash With U.S. Troops"
"American troops in Iraq had their first actual battle with ISIS troops after the Islamist militants tried to overrun a base, an encounter that left the ISIS troops decimated and in retreat. The attack took place near the Ein al-Asad base, which includes close to 100 U.S. military advisers. The U.S. troops, armed with 'light and medium weapons,' and were able to inflict casualties against the ISIS fighters, forcing them to retreat, Shafaq News reported. The American troops were also aided by fighter jets, which directed air strikes against the ISIS troops that 'silenced their heavy sources of fire.'"
That word decimate normally meaning one-in-ten but meaning much more than that within the military context.
Advisers armed with only "light and medium weapons" but presumably able to call on national assets if required. An AC-130 for instance.