From 673 till 693 there was civil war within Islam sparing Constantinople.
Prior to the Muslim invasion in Syria, the Jews and Christians had a mutual hatred of one another. In 634, orders were given for the forcible baptism of the Jews. As a result, the Jews aided the Muslim invaders.
A similar thing happened in Spain in 711, The Jews aided the Muslims who are today their biggest persecutors. They helped to create their biggest problem today.
From about 661 till 770 A. D. the house of Umayyad ruled the Islamic empire. The capital had been moved to Damascus from Medina. Here was the situation in Islam during this time.
1. Caliphs had brief reigns with intensive feuds and outbreaks of revolt.
2. Caliphs were frequently set up and taken down by the military. No official was trusted and even the caliph and his family were spied upon.
3. A struggle between the North Arabians and South Arabians spread throughout the entire Empire.
4. Africa, Spain, Iraq, and Khorasan were torn by dissension.
5. There were palace murders and dethronements.
6. Meanwhile the dispute between the Sunni and Shiites was heating up.
This period ended when Abul Abbas was proclaimed caliph as “As-Saffah” [The Shedder of Blood]. He was aptly named. He hunted down and killed all the members of the ruling house of Umayyad. The lone survivor fled to Spain where he gained supreme power. Abul Abbas destroyed the palaces and aqueducts in Damascus.
From that time the provinces of the Empire began to free themselves from the central political power. However, they remained loyal to its religious authority.
Baghdad became the capital of the Islamic Empire from 750 to 1258.