The Islamic conquests brought into being a new imperial system. The Muslims adopted the patterns of administration used by the Byzantines in Egypt and Syria and by the Sassanids in Persia. Specifically, Arab emirs, or governors, were appointed and given overall responsibility for public order, maintenance of the armed forces, and tax collection. Below them, experienced native officials remained in office. Thus there was continuity with previous administrations.

The Umayyad caliphate witnessed the further development of the imperial administration. At the head stood the caliph. Theoretically, he had the ultimate responsibility for the interpretation of the sacred law. In practice, however, the ulama interpreted the law as revealed in the Qur’an and the Sunna. In the course of time, the ulama’s interpretations constituted a rich body of law, the shari’a (shuh-REE-uh). The ulama enjoyed great prestige in the Muslim community and was consulted by the caliph on difficult legal and spiritual matters. The qadis (KAH-dees), or judges, who were well versed in the sacred law, carried out the judicial functions of the state.

The central administrative organ was the diwān, which collected the taxes that paid soldiers’ salaries (see “Reasons for the Spread of Islam”) and financed charitable and public works. Another important undertaking was a relay network established to rapidly convey letters and intelligence reports between the capital and distant outposts.

The early Abbasid period witnessed considerable economic expansion and population growth, complicating the work of government. New and specialized departments emerged, each with a hierarchy of officials. The most important new official was the vizier (vuh-ZEER), a position that the Abbasids adopted from the Persians. The vizier was the caliph’s chief assistant. Depending on the caliph’s personality, viziers could acquire extensive power, and some used their offices for personal gain.