As a state, the Roman Empire included large territorial possessions around the Mediterranean Sea in Europe, North Africa, and Western Asia, ruled by emperors. From the ascension of Caesar Augustus as the first Roman emperor until the military anarchy of the third century, the Roman Empire was a principate with Italy as the metropolis of its provinces and the city of Rome as the sole capital. Later, the empire was ruled by several emperors who shared control over the Western Roman Empire and the Eastern Roman Empire.
The predecessor state to the Roman Empire, the Roman Republic, which succeeded the Roman monarchy in the 6th century BC, was destabilized by a series of civil wars and political conflicts.