The Byzantine Empire had an absolute monarchy. Their government is also considered a Caesaropapism because the supreme ruler was secular. In the early days he was usually elected by the senate, the people, or the army, or all three. Later it became the custom to allow the son of an emperor (Porphyrogenite) to succeed to the throne and then to depose him if he proved to be weak or incompetent.
A reigning emperor was considered sacred and appointed by God and he was revered by his people in much the same way that their pre-Christian ancestors had worshipped the god-kings of ancient days. He lived in an elaborate palace, was surrounded by a lavish court, and took part in one complicated ceremonial event after another. In civil government the emperor was supreme, for he both made the laws and enforced them. His power over the church was almost as great; he appointed the patriarch of Constantinople who acted as head of the church in the east; he called church councils and published their decrees; and in general he directed the activities of the priests.
Round the person of the Emperor there revolved a whole world of court dignitaries and high officials, who formed the court and composed the members of the central government. Until towards the close of the sixth century, the Byzantine Empire had retained the Roman administrative system.
A small number of high officials, to whom all the services were subordinated, were at the head of affairs, and, after the example of Rome, the Byzantine Empire had maintained the old separation of civil and military powers and kept the territorial subdivisions due to Diocletian and Constantine. But during the course of the seventh and eighth centuries the administration of the Byzantine monarchy underwent a slow evolution. Civil and military powers became united in the same hands, but in new districts, the themes, which superseded the old territorial divisions.
Justinian reformed the government and ordered a review of Roman law. This undertaking led to the publication of the Code of Justinian, a digest of Roman and church law, texts, and other instructional materials that became the foundation of modern Western law. Justinian also participated actively in the religious arguments of his day.
In the capital near the sovereign, the heads of the great departments, the Ministers, if they may be so called, directed the government from above and transmitted the will of the Emperor throughout the entire realm. Since the seventh century the Byzantine Empire had gradually become Hellenized, and the Latin titles which were still borne by officials in the days of Justinian had assumed a purely Greek form.
Salvation appeared from the west when Heraclius (610-641), the Byzantine governor of North Africa, returned to Constantinople to overthrow the mad emperor Phocas. Conditions were so dismal and the future appeared so perilous when Heraclius arrived in the capital that he considered moving the government from Constantinople to Carthage in North Africa.