Hasan (häsänˈ) [key], c.625–c.669; son of Ali and Fatima (daughter of Muhammad the Prophet). When Ali was killed in 661, Hasan became caliph, but he was not strong enough to withstand the threat of arms of the Umayyads and under pressure abdicated in favor of Muawiya. He retired to Medina and died, reputedly of poison. His more active brother, Husein, took up the family cause. The Shiites believe that Hasan was murdered by the Umayyads and venerate him as a martyr.
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