Demographics of Iraq
97% of Iraqis follow Islam: 61% Shia and 34% Sunni. 1% of these describe themselves as "Just a Muslim". According to the CIA Factbook, Shias make up 60% of population, while Sunnis 35%. Christianity accounts for 5%, and the rest practice Mandaeism, Yazidism and other religions.
Demographics of Syria
According to Dr. Pierre Beckouche, before 2011, Sunni Muslims accounted for 74% of Syria's population, which included 500,000 Palestinan refugees and the non-Arab Sunni Muslims, namely the Kurds (9-10%) and the Turkmen/Turkoman (4%). Other Muslims included Shias and Alawites (11%-16%), whilst the Christians made up 10% of the population. There were also a few Jewish communities in Aleppo and Damascus.