Turkish Foreign Minister Ahmet Davutoglu said this month that the missile batteries will stay only as long as there is a threat.

The Syrian crisis started nearly two years ago, when President Bashar al-Assad's forces cracked down on civilians peacefully protesting government policies.

The violence led to an armed uprising and escalated into a civil war, with al-Assad trying to defend four decades of family rule against rebels demanding his ouster.

But with neither side showing any indication of backing down, it's unclear how many more thousands of civilians may die.