Abu al-'Abbas as-Saffah dies in 754, after…

Abu al-'Abbas as-Saffah dies in 754, after only five years as caliph; the main burden of establishing the 'Abbasid caliphate thus falls upon his brother Abu Jafar al-Mansur.

Al-Mansur becomes the second caliph of the Abbasid dynasty and leader of the Asian and eastern Mediterranean Muslim community.

The Abbasid rulers reassert the theocratic concept of the caliphate and continuity with orthodox Islam as the foundation for unity and authority in the empire.

Abbasid leadership also renders Islam and the fruits of power accessible to non-Arabs; Iranians become prominent in the new caliphal government and administration.

Al-Mansur faces opposition, however, from Iran and from the Shiite Muslim sect.

Al-Mansur is largely responsible for cutting the 'Abbasids free from the movement that has brought them to power, and is involved in the murder of several leading personalities in that movement.

A danger to al-Mansur's caliphate comes from a number of revolts by ambitious army commanders.

The most serious of these is the revolt in 754 of al-Mansur's uncle, 'Abd Allah, who thinks he has better claims to the caliphate than his nephew.

The danger is only averted with the help of Abu Muslim.

Although the 'Abbasid's enthronement was largely due to Abu Muslim's military victories and political prowess, they have quickly become leery of a vassal with so much power and popularity.

With the accession of the morbidly suspicious al-Mansur, Abu Muslim's downfall is sealed.

After having Abu Muslim quell an uprising led by a rebellious uncle, al-Mansur strips away the governorship of Khorasan from him.

When Abu Muslim arrives at court, al-Mansur has him treacherously put to death, thus eliminating a potential rival for the throne.

The unavenged death of Abu Muslim, already a legendary hero to the population, inspires many later uprisings and revolts.