How Large Was the Roman Empire?
The Roman Empire reached its maximum size under the Emperor Trajan (AD 98-117). In his reign Rome’s direct rule extended over an area bounded by Britain, Spain, the Rhine, Dacia (a country north of the Lower Danube), the Euphrates and the Sahara.
In the far north the frontier was Hadrian’s Wall in Britain and then the wall of Antonius Pius, which ran from the Firth of Forth to the mouth of the Clyde. Little is known about Rome before about 400 BC, by which time the city had already become a republic. Despite setbacks, the city gradually extended its sway over the whole of central and northern Italy. Victory over the Greek city-state of Tarentum (modern Taranto) in 274 BC, led to Southern Italy being added to the Roman dominions.
In 264 BC began the series of Punic Wars between Rome and the city of Carthage in North Africa to decide the supremacy of the Mediterranean. When the first one ended in 241 BC, the Romans acquired Sicily, Sardinia, Corsica and later the Po valley, or Cisalpine Gaul. The second also ended in victory for the Romans when they beat Hannibal at Zama in 202 BC. In the rapid expansion that followed, Macedonia and Corinth in Greece and Pergamum in Asia Minor came under Roman rule.
In 75 BC, Bithynia and other states of Asia Minor became provinces of Rome after a war with Mithridates, King of Pontus. Julius Caesar, made proconsul or governor of Cisalpine Gaul, used this position to conquer the whole of Gaul in 58-51 BC. After Caesar’s assassination a struggle developed between Octavian and Antony, who was allied with Cleopatra of Egypt. Octavian crushed them at Actium in 31 BC and Egypt also became a Rome province.
In the intervening years, the Romans annexed Cappadocia (in Asia Minor, west of the Euphrates), Mauretania (modern Morocco), Thrace (in the Balkan Peninsular) and Lydia (on the west coast of Asia Minor). Claudius conquered Britain in AD 41-54. The Flavian Emperors (AD 69-96) extended the Syrian frontier and introduced Roman civilization to southern Germany. Finally, Trajan annexed Dacia, temporarily occupied Armenia and Mesopotamia and enlarged the realms of Rome to their greatest extent.