http://www.aljazeera.com/news/2016/05/syria-civil-war-explained-160505084119966.html
Initially, lack of freedoms and economic woes fuelled resentment of the Syrian government, and public anger was inflamed by the harsh crackdown on protesters. Successful uprisings in Tunisia and Egypt energised and gave hope to Syrian pro-democracy activists. Many Islamist movements were also strongly opposed to the Assads’ rule.
In 1982, Bashar’s father, Hafez al-Assad, ordered a military crackdown on the Muslim Brotherhood in Hama, which killed between 10,000-40,000 people and flattened much of the city.
Although the initial protests in 2011 were mostly non-sectarian, armed conflict led to the emergence of starker sectarian divisions. Minority religious groups tend to support the Assad government, while the overwhelming majority of opposition fighters are Sunni Muslims.
Most Syrians are Sunni Muslims, but Syria’s security establishment has long been dominated by members of the Alawite sect, of which Assad is a member.