The vastness and diversity of the territories governed by Islamic dynasty was stretched from the Moroccan shores of the Mediterranean to northern India.
In the early 600s the centuries-old conflict between the Byzantines and the Sasanians was being fought with particular intensity. The Sasanian emperor Khusraw II, captured Jerusalem in 614 and briefly occupied Egypt in 619. The Byzantine emperor Heraclius subsequently led a successful counter_offensive which carried him as far as Ctesiphon, which he sacked in 628. The squandering of military and financial resources in these campaigns must certainly have played a role in crucially weakening the two empires and laid them open to attack from the Muslim Arab armies, which began operating out of the Arab peninsula from the 630s onwards.

The rise of Islam

The Prophet Muhammad was born in either AD 570 or 571 in Mecca.
Around 610 the Prophet received the first of a series of visionary revelations from the Archangel Gabriel who in subsequent visions was to dedicate to him the entirety of the Koran - the word of God as communicated to the Prophet.

Part of Islam's strong appeal to its early converts was its simplicity and austerity.
The number of Islam's converts and military successes was unprecedented. By the time of Muhammad's death in 632, his followers were in control of the cities of Mecca and Medina, and much of Western Arabia. Under the caliphs who succeeded him, Muslim Arab armies defeated the Byzantines at Ajnadayn in southern Palestine in 634 and the Sasanians at Qadisiyya in southern Mesopotamia in 636, thus conquering a spread of land that included Palestine, Syria, Iraq, and most of Iran.

The Umayyad and Abbasid Dynasties

This was only by the assassination of Ali in 661, after which Muawiya made the caliphate the possession of his clan, the Umayyads, from 661 to 750.
Armies sent out by the Umayyad caliphs continued to add to the territories of Islam. North Africa was conquered in the late seventh century, Transoxania (the region beyond the River Oxus) in the early eighth, an Arab army reached the Indus in 710 and in central Asia Muslims defeated the Chinese at the Battle of Talas in 751. They acquired an empire that stretched from the Atlantic to the edges of China and India.

In 750 the Umayyads were overthrown by a rebellion that began in Khurasan (eastern Iran) and culminated in the succession to the caliphate of the Abbasid dynasty. The Abbasids transferred the seat of government from the Umayyad capital of Damascus in Syria to a new capital in Baghdad, some 35 miles (56 km) away from the old Sasanian capital of Ctesiphon.
Symbolically, the caliph had placed himself in the centre of Baghdad, which in turn was the centre of the world.
The Abbasid caliphs used increasing numbers of mamluks, or slave soldiers, in their armies, and in 836 tensions between these mamluks and citizens of Baghdad led to the removal of the capital from Baghdad to Samarra. Yet though Samarra was the cultural capital of the Islamic world.

Islamic Art
Robert Irwin