In historiography, ancient Rome describes Roman civilization from the founding of the Italian city of Rome in the 8th century BC to the collapse of the Western Roman Empire in the 5th century AD, in turn encompassing the Roman Kingdom (753–509 BC), Roman Republic (509–27 BC) and Roman Empire (27 BC–476 AD) until the fall of the western empire. The civilisation began as an Italic settlement in the Italian Peninsula, traditionally dated to 753 BC, that grew into the city of Rome and which subsequently gave its name to the empire over which it ruled and to the widespread civilisation the empire developed. The civilization was led and ruled by the Romans, alternately considered an ethnic group or a nationality. The Roman Empire expanded to become one of the largest empires in the ancient world, still ruled from the city, with an estimated 50 to 90 million inhabitants (roughly 20% of the world's population at the time) and covering 5 million square kilometres (1.9 million square miles) at its height in AD 117.
In its many centuries of existence, the Roman state evolved from an elective monarchy to a democratic classical republic and then to an increasingly autocratic semi-elective military dictatorship during the Empire. Through conquest, cultural, and linguistic assimilation, at its height it controlled the North African coast, Egypt, Southern Europe, and most of Western Europe, the Balkans, Crimea and much of the Middle East, including Anatolia, Levant and parts of Mesopotamia and Arabia. It is often grouped into classical antiquity together with ancient Greece, and their similar cultures and societies are known as the Greco-Roman world.
Ancient Roman civilisation has contributed to modern language, religion, society, technology, law, politics, government, warfare, art, literature, architecture and engineering. Rome professionalised and expanded its military and created a system of government called res publica, the inspiration for modern republics such as the United States and France. It achieved impressive technological and architectural feats, such as the construction of an extensive system of aqueducts and roads, as well as the construction of large monuments, palaces, and public facilities.
The Punic Wars with Carthage were decisive in establishing Rome as a world power. In this series of wars, Rome gained control of the strategic islands of Corsica, Sardinia, and Sicily; took Hispania (modern Spain and Portugal); and destroyed the city of Carthage in 146 BC, giving Rome supremacy in the Mediterranean. By the end of the Republic (27 BC), Rome had conquered the lands around the Mediterranean and beyond: its domain extended from the Atlantic to Arabia and from the mouth of the Rhine to North Africa. The Roman Empire emerged with the end of the Republic and the dictatorship of Augustus. Seven-hundred and twenty-one years of Roman–Persian Wars started in 92 BC with the first struggle against Parthia. It would become the longest conflict in human history, and have major lasting effects and consequences for both empires.
Under Trajan, the Empire reached its territorial peak. It stretched from the entire Mediterranean Basin to the beaches of the North Sea in the north, to the shores of the Red and Caspian Seas in the East. Republican mores and traditions started to decline during the imperial period, with civil wars becoming a prelude common to the rise of a new emperor. Splinter states, such as the Palmyrene Empire, would temporarily divide the Empire during the crisis of the 3rd century before some stability was restored in the Tetrarchy phase of imperial rule.
Plagued by internal instability and attacked by various migrating peoples, the western part of the empire broke up into independent barbarian kingdoms in the 5th century.[a] The eastern part of the empire remained a power through the Middle Ages until its fall in 1453 AD.