The revolt against Syria's President Bashar Assad, inspired by uprisings which toppled three Arab leaders in 2011, has taken a sectarian slant as most of the protesters trying to topple the president are Sunnis.
Assad is from Syria's minority Alawite sect and critics say the president has filled senior political and military posts with Alawites to impose his rule through sectarian loyalty.
The Alawite sect
Sunnis Muslims make up 74 percent of Syria's 22 million population, Alawites 12 percent, Christians 10 percent and Druze 3 percent. Ismailis, Yezidis and a few Jews make up the rest.
The clannishness, secrecy and tenacity of Syria's power elite around Assad have deepened Sunni Muslim suspicions about the enigmatic Alawite faith.
An oppressed minority for most of their history, Alawites suddenly cemented their control in Syria in 1970 when Assad's father Hafez staged a coup that sidelined the Sunnis. He built a ferocious security apparatus based on fellow Alawite officers.
Allying with Sunni merchant classes in Damascus and Aleppo, the Alawite elite expanded their influence to the economy as well as the security apparatus and the military. The core of the feared pro-Assad Shabiha militia is Alawite.
This year's bloody struggle between Assad forces and pro-democracy protesters splits Syria along a minority-majority gulf made deeper by the fact many Sunnis call Alawites heretics.
Like most Arab countries, Syria has seen conservative Islam spreading in recent decades. This has sharpened Sunni differences with the Alawites, who claim to be mainline Shi'ites and sometimes copy Sunni practices to play down differences.
Sectarian killings have racked the central city of Homs, and Alawites have been targeted because they were the same sect as the president. Many Alawites live around or in Homs and Hama, another restive city, and the port of Latakia.
Not all Alawites support the Assad dynasty and only a few have profited from Assad's rule, with many living in poverty in Syria's central mountains. The sect extends north to the Turkish city of Antakya, near the ancient city of Antioch, in Turkey where there are up to 12 million Alawites.
The Alawite religion is often called "an offshoot of Shi'ism", Islam's largest minority sect, but that is something like referring to Christianity as "an offshoot of Judaism".
Alawites broke away from Shi'ism more than 1,000 years ago and retain some links to it, including the veneration of Ali, the cousin and son-in law of the Prophet Mohammad. Alawi literally means "those who adhere to the teachings of Ali".
But several beliefs differ sharply from traditional Islam. Named after Ali, Alawites believe he was divine, one of many manifestations of God in a line with Adam, Jesus, Mohammad, Socrates, Plato and some pre-Islamic sages from ancient Persia.
To orthodox Muslims, this eclectic synthesis of Christian, Gnostic, Neoplatonic and Zoroastrian thought violates Islam's key tenet that "there is no God but God".
Alawites interpret the Pillars of Islam (the five duties required of every Muslim) as symbols rather than duties. They celebrate a group of holidays, some Islamic, some Christian, and many Alawite practices are secret. They consider themselves to be moderate Shi'ites.
History and lifestyle
Oppressed during the Ottoman period, Alawites have played down their distinctive beliefs in recent decades to argue they were mainline Shi'ites like in Iran. This is partly to satisfy the constitutional rule that the president must be a Muslim.
The outlawed Muslim Brotherhood called Alawites infidels for decades. Leaders of the Sunni movement no longer say this openly, but nobody knows whether the rank and file is convinced.
Isolated in the mountains near Syria's Mediterranean coast, Alawites taught that the Koran was to be read allegorically and preferred to pray at home rather than in mosques.
They were also highly secretive, initiating only a minority of believers into their core dogma, including reincarnation and a divine Trinity, and into rituals including a rite of drinking consecrated wine similar to a Christian Mass.
French colonial administrators tried to classify Syrian Alawism as a separate religion despite resistance from Alawi leaders who were more interested in identifying with Islam.
Like the nearby Druze, Alawites adopted the Shi'ite practice of taqiyya, or hiding their beliefs to avoid persecution. "Taqiyya makes a perfect qualification for membership in the mukhabarat, the ubiquitous intelligence/security apparatus that has dominated Syria's government for more than four decades," the British Islam expert Malise Ruthven wrote recently.