NEAR the Yarmouk River, along what is today the border between Syria and Jordan, south-east of the Sea of Galilee. The result of the battle was a complete Muslim victory which ended Byzantine rule in Syria. The Battle of Yarmouk is regarded as one of the most decisive battles in military history, and it marked the first great wave of Islamic conquests after the death of Muhammad, heralding the rapid advance of Islam into the then Christian Levant._x005F_x000D_In order to check the Muslim advance and to recover lost territory, Emperor Heraclius had sent a massive expedition to the Levant in May 636. As the Byzantine army APPROACHED, the Muslims retreated from Syria and regrouped all their forces at the Yarmouk plains close to Arabia where, after being REINFORCED, they defeated the numerically superior Byzantine army. The battle is also considered to be one of Khalid ibn al-Walid’s GREATEST military victories. It cemented his reputation as one of the greatest tacticians and cavalry commanders in history. Caliph Abu Bakr died in 634. His successor, Umar, was determined to continue the Caliphate Empire’s expansion deeper into Syria. Though previous campaigns led by Khalid were successful, he was replaced by Abu Ubaidah. Having secured southern Palestine, Muslim forces now advanced up the trade route where Tiberias and Baalbek fell without much struggle and the Muslims conquered Emesa early in 636. From thereon, the Muslims continued their conquest ACROSS the Levant.