Khalid ibn Walid was from the Meccan tribe of Quraish, who opposed Muhammad, and he played a vital role in their victory at the Battle of Uhud. He accepted Islam, however, and joined Muhammad after the Treaty of Hudaybiyyah and commanded various expeditions for him, such as the Battle of Mu'tah. After Muhammad's death, he played a key role in commanding Medinan forces for Abu Bakr in the Ridda wars, the capture of the Sassanid Arab client Kingdom of Al-Hirah, and the defeat of the Sassanid Persian forces during his conquest of the Persian Empire. He then crossed the desert to capture the Byzantine Arab client state of the Ghassanids during his conquest of Roman Syria. Even though Umar later relieved him of high command, he remained the effective leader of the forces arrayed against the Byzantines during the early stages of the Byzantine-Arab Wars. Under his command, Damascus was captured in 635 and the key Arab victory against the Roman Byzantine forces was achieved at the Battle of Yarmuk (636), which led to the conquest of the Bilad al-Sham (Levant).
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