In the course of history, wars between the Byzantines and the Persians had been fought every now and then. In these wars sometimes the Persians had the upper hand and sometimes the Byzantines had the upper hand. In the early years of the seventh century the Persians defeated the Byzantines. As the Christians were monotheists, the pagans of Arabia hailed the victory of the Persians over the Christian Byzantines. At that time the Holy Prophet prophesied that within ten years the tables would be turned, and the Byzantines would defeat the Persians. This prophecy was fulfilled, and in the later twenties of the seventh century the Byzantine emperor Heracleus inflicted a crushing defeat on the Persians. It was at this stage of the Perso-Byzantine conflict that Islam rose into power. The Byzantines could not view the growing strength of Islam with favor. It was accordingly apprehended that after defeating the Persians the Byzantine emperor Heracleus would invade Arabia. After the conquest of Makkah when Islam came to spread throughout Arabia, the invasion of Arabia by the Byzantines appeared to be imminent. It was rumored that the Byzantine emperor was mustering a large army in Syria to invade Arabia.