Editing Roman Empire (section)

== History ==
Rome expanded beyond central Italy during the period of the Roman Republic. By the first century BC, Roman authority covered the Italian Peninsula, much of the western Mediterranean, Greece, parts of the Balkans, North Africa, and territories in western Asia. Military expansion brought wealth and land into Roman control, but it also increased political competition between commanders and contributed to a series of civil wars.

Julius Caesar became dictator after defeating his opponents but was assassinated in 44 BC. His adopted heir Octavian joined Mark Antony and Marcus Aemilius Lepidus in the Second Triumvirate. The alliance defeated the assassins of Caesar before breaking apart. Octavian defeated Antony and Cleopatra at the Battle of Actium in 31 BC and annexed Egypt the following year.

In 27 BC, the Roman Senate granted Octavian the title Augustus. He retained republican offices and institutions while holding control over the army, important provinces, taxation, and senior appointments. This system became known as the Principate. The Senate, magistrates, and assemblies continued to exist, but political authority increasingly depended on the emperor.

The reign of Augustus began a long period of internal stability commonly called the Pax Romana. The Julio-Claudian, Flavian, and Nerva–Antonine dynasties extended Roman administration and developed cities, roads, aqueducts, ports, and frontier defences. Britain was invaded under Claudius, while Trajan conquered Dacia and temporarily extended Roman authority into Mesopotamia. Roman expansion incorporated Greece and much of the Balkans into a political and transport system based around the Mediterranean.<ref name="southern-europe-history"/><ref name="balkans-history"/>

Territorial expansion largely stopped after the reign of Trajan. [[Hadrian]] withdrew from several eastern conquests and concentrated on securing the frontiers. Defensive systems were established along the Rhine, Danube, northern Britain, North Africa, and the eastern border with the Parthian and later Sasanian empires.

The empire entered a period of political instability during the third century. Emperors were frequently removed by military revolt, frontier invasions increased, and separate governments developed in Gaul and the eastern provinces. Economic disruption, disease, civil war, and pressure on the army weakened central authority. Emperor [[Aurelian]] restored the breakaway territories during the 270s.

[[Diocletian]] reorganized the government after becoming emperor in AD 284. He divided imperial responsibility among several rulers in a system known as the Tetrarchy. The provinces were reorganized into smaller administrative units, taxation was revised, and the size of the government and military increased. The Tetrarchy did not create a lasting system of peaceful succession, and renewed civil wars followed Diocletian's retirement.

[[Constantine the Great]] defeated his rivals and reunited the empire under one ruler. In AD 330, he inaugurated Constantinople on the site of Byzantium as an imperial capital. Its location on the [[Bosporus]] placed it between the Balkans, Anatolia, the Black Sea, and the eastern Mediterranean. Anatolia and Thrace later became central territories of the eastern Roman administration.<ref name="turkey-history"/>

Theodosius I was the final emperor to govern both the western and eastern courts. After his death on 17 January AD 395, authority passed to his sons. [[Honorius]] governed the west, while [[Arcadius]] governed the east. The two administrations continued to regard themselves as parts of the same Roman state but developed separate courts, armies, finances, and political interests.