Iran replace Sunni with Shia population in Syria

The population swaps are central to a plan to make demographic changes to parts of Syria, realigning the country into zones of influence that backers of Bashar al-Assad, led by Iran, can directly control and use to advance broader interests. Iran is stepping up its efforts as the heat of the conflict starts to dissipate and is pursuing a very different vision to Russia, Assad’s other main backer. 

Source 

https://www.theguardian.com/world/2017/jan/13/irans-syria-project-pushing-population-shifts-to-increase-influence