The Romans conquered most of this during the Republic , and it was ruled by emperors following Octavian 's assumption of effective sole rule in 27 BC. The western empire collapsed in AD, but the eastern empire lasted until the fall of Constantinople in By BC, the city of Rome had expanded its rule to most of the Mediterranean and beyond.
However, it was severely destabilised by civil wars and political conflicts , which culminated in the victory of Octavian over Mark Antony and Cleopatra at the Battle of Actium in 31 BC, and the subsequent conquest of the Ptolemaic Kingdom in Egypt.
In 27 BC, the Roman Senate granted Octavian overarching military power imperium and the new title of Augustus , marking his accession as the first Roman emperor. The vast Roman territories were organized into senatorial provinces, governed by proconsuls who were appointed by lot annually, and imperial provinces, which belonged to the emperor but were governed by legates.
The first two centuries of the Empire saw a period of unprecedented stability and prosperity known as the Pax Romana lit. Rome reached its greatest territorial extent under Trajan r. In the 3rd century, the Empire underwent a year crisis that threatened its existence due to civil war, plagues and barbarian invasions.
The Gallic and Palmyrene empires broke away from the state and a series of short-lived emperors led the Empire, which was later reunified under Aurelian r.
