It occurred in the eighth year of Hijrah in 629 CE. This is the period in which Muhammad and his followers journeyed from Mecca to Medina. It was a battle between Muhammad's forces and the army of the Byzantine Empire east of the Jordan River near the town of Mutah. The battle was in reaction to the Eastern Roman Empire's forces killing some of Muhammad's emmisaries. It was the largest battle, up till that time, between the Muslims and the Christians.