You cannot defeat Islamic State with airstrikes only. It's necessary to cooperate with ground troops, and the Syrian army is the most efficient and powerful ground force to fight the Islamic State.
”PUTIN AND HIS WARS-SYRIA,UKRAINE AND…..-PSYCHIC PREDICTIONS TO BASHAR AL-ASSAD,SERGEI LAVROV,YULYA TYMOSHENKO,VAGIT ALEKPEROV(THE PRESIDENT OF LUKOIL) AND….: Clairvoyant/Psychic predictions -Ukraine