Russian boots is what it will take.
Spetsnaz boots are there and the Assad opposition militias are losing key leaders at a high rate.... Very good intelligence and targeting
Putin will use the indigenous regional armies ( Syria and Iran) as the grunt boots ... Very smart on so many levels. He remembers the lessons of Afghanistan. The locals will support or tolerate their own arab and even Shia Muslim armies fighting as seculars, will turn against white Russians labeled by their religious leaders as invaders and crusaders