The successor of Abu-Bekr, and the second Caliph from 634 to 644; was at first a persecutor of the Faithful, but underwent in 615 a sudden conversion like Said, with a like result; was vizier of Abu-Bekr before he succeeded him; swept and subdued Syria, Persia, and Egypt with the sword in the name of Allah, but is accused of having burned the rich library of Alexandria on the plea that it contained books hostile to the faith of Islam; he was an austere man, and was assassinated by a Persian slave whose wrongs he refused to redress.