section_path: Succession
section_name: Succession
paragraph_text: Succession
  
  With Muhammad's death, disagreement broke out over who his successor would be. Umar ibn al-Khattab, a prominent companion of Muhammad, nominated Abu Bakr, Muhammad's friend and collaborator. With additional support, Abu Bakr was confirmed as the first caliph. This choice was disputed by some of Muhammad's companions, who held that Ali ibn Abi Talib, his cousin and son-in-law, had been designated the successor by Muhammad at Ghadir Khumm. Abu Bakr immediately moved to strike against the Byzantine (or Eastern Roman Empire) forces because of the previous defeat, although he first had to put down a rebellion by Arab tribes in an event that Muslim historians later referred to as the Ridda wars, or "Wars of Apostasy".
  
  The pre-Islamic Middle East was dominated by the Byzantine and Sassanian empires. The Roman–Persian Wars between the two had devastated the region, making the empires unpopular amongst local tribes. Furthermore, in the lands that would be conquered by Muslims, many Christians (Nestorians, Monophysites, Jacobites and Copts) were disaffected from the Eastern Orthodox Church which deemed them heretics. Within a decade Muslims conquered Mesopotamia, Byzantine Syria, Byzantine Egypt, large parts of Persia, and established the Rashidun Caliphate.