Princeps in the context of "Octavius Mamilius"

The history of the Roman Empire covers the history of ancient Rome from the traditional end of the Roman Republic in 27 BC until the abdication of Romulus Augustulus in AD 476 in the West, and the Fall of Constantinople in the East in 1453. Ancient Rome became a territorial empire while still a republic but was then ruled by emperors, beginning with Octavian Augustus, the final victor of the republican civil wars.

Rome had begun expanding shortly after the founding of the Republic in the 6th century BC, though it did not expand outside the Italian Peninsula until the 3rd century BC, during the Punic Wars, after which the Republic expanded across the Mediterranean. Civil war engulfed Rome in the mid-1st century BC, first between Julius Caesar and Pompey, and finally between Octavian (Caesar's grand-nephew) and Mark Antony. Antony was defeated at the Battle of Actium in 31 BC, leading to the annexation of Egypt. In 27 BC, the Senate gave Octavian the titles of Augustus ("venerated") and Princeps ("foremost"), thus beginning the Principate, the first epoch of Roman imperial history. Augustus' name was inherited by his successors, as well as his title of Imperator ("commander"), from which the term "emperor" is derived. Early emperors avoided any association with the ancient kings of Rome, instead presenting themselves as leaders of the Republic.

Primus inter pares is a Latin phrase meaning first among equals. It is typically used as an honorary title for someone who is formally equal to other members of their group but is accorded unofficial respect, traditionally owing to their seniority in office.

Historically, the princeps senatus of the Roman Senate was such a figure and initially bore only the distinction that he was allowed to speak first during debate. After the fall of the Republic, Roman emperors initially referred to themselves only as princeps despite having enormous power.

The Roman emperor was the ruler and monarchical head of state of the Roman Empire, starting with the granting of the title augustus to Octavian in 27 BC. The title of imperator, originally a military honorific, was usually used alongside caesar, originally a cognomen. When a given Roman is described as becoming emperor in English, it generally reflects his accession as augustus, and later as basileus. Early emperors also used the title princeps ("first one") alongside other Republican titles, notably consul and pontifex maximus.

The legitimacy of an emperor's rule depended on his control of the Roman army and recognition by the Senate; an emperor would normally be proclaimed by his troops, or by the Senate, or both. The first emperors reigned alone; later emperors would sometimes rule with co-emperors to secure the succession or to divide the administration of the empire between them. The office of emperor was thought to be distinct from that of a rex ("king"). Augustus, the first emperor, resolutely refused recognition as a monarch. For the first three hundred years of Roman emperors, efforts were made to portray the emperors as leaders of the Republic, fearing any association with the kings who ruled Rome prior to the Republic.

During the Roman Empire, the governor of Roman Egypt (praefectus Aegypti) was a prefect who administered the Roman province of Egypt with the delegated authority (imperium) of the emperor.

Egypt was established as a Roman province in consequence of the Battle of Actium, where Cleopatra as the last independent ruler of Egypt and her Roman ally Mark Antony were defeated by Octavian, the adopted heir of the assassinated Roman dictator Julius Caesar. Octavian then rose to supreme power with the title Augustus, ending the era of the Roman Republic and installing himself as princeps, the so-called "leading citizen" of Rome who in fact acted as an autocratic ruler. Although senators continued to serve as governors of most other provinces (the senatorial provinces), especially those annexed under the Republic, the role of Egypt during the civil war with Antony and its strategic and economic importance prompted Augustus to ensure that no rival could secure Aegyptus as an asset. He thus established Egypt as an imperial province, to be governed by a prefect he appointed from men of the equestrian order.

The Roman imperial cult (Latin: cultus imperatorius) identified emperors and some members of their families with the divinely sanctioned authority (auctoritas) of the Roman State. Its framework was based on Roman and Greek precedents, and was formulated during the early Principate of Augustus. It was rapidly established throughout the Empire and its provinces, with marked local variations in its reception and expression.

Augustus's reforms transformed Rome's Republican system of government to a de facto monarchy, couched in traditional Roman practices and Republican values. The princeps (emperor) was expected to balance the interests of the Roman military, Senate and people, and to maintain peace, security and prosperity throughout an ethnically diverse empire. The official offer of cultus to a living emperor acknowledged his office and rule as divinely approved and constitutional: his Principate should therefore demonstrate pious respect for traditional Republican deities and mores.

Tiberius Julius Caesar Augustus (/taɪˈbɪəriəs/ ty-BEER-ee-əs; 16 November 42 BC – 16 March AD 37) was Roman emperor from AD 14 until 37. He succeeded his stepfather Augustus, the first Roman emperor. Tiberius was born in Rome in 42 BC to Roman politician Tiberius Claudius Nero and his wife, Livia Drusilla. In 38 BC, Tiberius's mother divorced his father and married Augustus. Following the untimely deaths of Augustus's two grandsons and adopted heirs, Gaius and Lucius Caesar, Tiberius was designated Augustus's successor. Prior to this, Tiberius had proved himself an able diplomat and one of the most successful Roman generals. His conquests of Pannonia, Dalmatia, Raetia, and (temporarily) parts of Germania laid the foundations for the empire's northern frontier.

Early in his career, Tiberius was happily married to Vipsania, daughter of Augustus's friend, distinguished general and intended heir, Marcus Vipsanius Agrippa. They had a son, Drusus Julius Caesar. After Agrippa died, Augustus insisted that Tiberius divorce Vipsania and marry Agrippa's widow, Augustus' own daughter (Tiberius's step-sister) Julia. Tiberius reluctantly gave in. This second marriage proved scandalous, deeply unhappy, and childless; ultimately, Julia was sent into exile by her father. Tiberius adopted his nephew, the able and popular Germanicus, as heir. On Augustus's death in 14, Tiberius became princeps at the age of 55. He seems to have taken on the responsibilities of head of state with great reluctance and perhaps a genuine sense of inadequacy in the role, compared to the capable, self-confident and charismatic Augustus.