In the late 620s, the Islamic Prophet Muhammad had already managed to unify much of Arabia under Muslim rule via conquest as well as making alliances with neighboring tribes, and it was under his leadership that the first Muslim-Byzantine skirmishes took place. Just a few months after Emperor Heraclius and the Persian general Shahrbaraz agreed on terms for the withdrawal of Persian troops from occupied Byzantine eastern provinces in 629, Arab and Byzantine troops confronted each other at the Mu'tah in response to the murder of Muhammad's ambassador at the hands of the Ghassanids, a Byzantine vassal kingdom. Muhammad died in 632 and was succeeded by Abu Bakr, the first Caliph with undisputed control of the entire Arabian Peninsula after the successful Ridda wars, which resulted in the consolidation of a powerful Muslim state throughout the peninsula.