Arab Invasions: The Caliphate Looks East (8th CE - 11th CE)
The year 628 CE was momentous for the Sassanian Empire. It marked the end of the rule of Khusrow II Parviz, the last great Sassanid Emperor of Persia. He had brought great peace and an end to the war with the Byzantines, and had married Maria, Princess of Constantinople. With his death came a terrible succession war in Persia for the next 4 years. Ultimately, Yezdegird II Sheriyar (632-641 CE) ascended the throne in 632 CE. He was to be the last Sassanid Emperor.
Deep in the heart of Arabia, something was stirring. In 622 CE, Mohammed the Prophet of Islam, performed the Hejira, the return to Arabia, Medina to be precise, from Abyssinia (Ethiopia). He established the Constitution of Medina and forged the young Islamic nation-state in a series of battles and offensives. By 629 CE, he had taken Mecca, the holiest city in Arabia, and by 632 CE at the age of 62, he had united all the Arab tribes under one banner and one religion. His death in 632 CE, and that of his successor Abu Bakr in 634 CE, led to Umar taking charge of the caliphate, and he soon sent the fractious armies of Islam on a conquest against their neighbours, the Byzantines and the Persians.