Islam's second caliph, who was credited with extensive Arab conquests. Hazrat Umar's dramatic conversion to Islam in 615 was regarded as the turning point of Islam. He gave his daughter Hafsa to the Prophet (PBUH) as a bride. But his true mettle was proved when he became a caliph in 634. The Prophet (PBUH) gave him the title of al-Farouq. Hazrat Umar's army, led by the famous General Khalid bin Walid, captured Damascus in 635 and in 636 smashed the Byzantine Army at the battle of Yarmuk. Jerusalem was captured in 638. Another section of his army was driving the Iranians from Iraq. The victory at Qadisiya in 636 left the Sassanian capital Ctesiphon virtually defenceless. Once the Syrian army was free to attack upper Mesopotamia from the west, it came under the control of the Caliph in 640. Hazarat Umar founded Basra and Kufa in 635. Between 639 and 642, the Arabs succeeded in driving the Byzantine from Egypt. Hazrat Umar was not only a conqueror, but also proved a great administrator. He was the first to be called Amir-ul-Mominain. In general his policy was to leave the conquered people in possession of their lands, in exchange of payment of tribute, which made Muslims economically powerful. 36,000 towns came under Muslim domination during his reign, which lasted for about ten years. An Iranian slave named Firoz while saying his morning prayers stabbed him to death. Hazrat Usman succeeded him.