Shiism

Shiism reveres Ali ibn Abi Talib as Muhammad's cousin and son-in-law, and holds that his descendants, the Imams, are infallible guides. The martyrdom of Husayn at Karbala in 680 is mourned every year on Ashura.

The main branches differ over the line of Imams. Twelvers recognise twelve, the last of whom, the Mahdi, lives hidden in occultation; Ismailis follow Ismail ibn Jafar; Zaydis, the closest to Sunnism, are found in the highlands of Yemen.

In 1337 the Sarbadars, a Shia-ruled state, were newly established at Sabzevar in Khorasan. The great turning point came in 1501, when Ismail I made Twelver Shiism the official religion of Safavid Iran and a largely Sunni population was converted, often by force. After the Safavids fell in 1736, the Usuli school gained ground over the Akhbari.