Roman history falls into three distinct periods designated by the form of government in use during each era: the monarchy, the republic, and the empire. In Roman tradition, the city of Rome was founded in 753 bc by Romulus and Remus, twin offspring of the god Mars. Romulus promptly murdered his brother to become the first king of Rome. According to legend, Rome had a sequence of seven kings, and during this period many of the religious and cultural institutions of Rome were established. For most of the monarchy (753-509 bc), Rome was simply one of hundreds of small city-states in Italy, often under the control of more powerful neighbors such as the Etruscans. The last kings of Rome, in fact, seem to have been Etruscans, but in 509 bc there was a revolution; the last Etruscan king. Tar-quin the Proud, was expelled from Rome; and the Roman Republic (509-31 bc) was established.
Over the next several hundred years, Rome began a gradual process of military expansion into the rest of Italy. This was a time of nearly constant warfare, and while the Romans were not superior to their enemies in either technology or tactics, they did practice a unique policy in their treatment of conquered cities. Rather than destroying them and enslaving the populace, the Romans granted full, or more commonly, partial citizenship or allied status to the captured peoples and demanded in return only that they contribute troops to the Roman army. This gave Rome enormous manpower reserves to draw upon, and many future wars would be won Through a combination of determination and manpower. Over this same period, the Roman constitution developed, consisting of a system of annually elected magistrates, a legal code, and a kind of balance of powers among different organs of the state. The top position in government was held by two magistrates known as consuls, and former magistrates became members of the senate, whose deliberations carried great influence.
By the middle of the third century bc, Roman consolidation of Italy was largely complete and Rome soon became embroiled, whether by accident or design, in a series of wars with overseas enemies. The most significant of these were the Punic Wars, fought against another young, expanding empire in the western Mediterranean: the North African city of Carthage. In the Second Punic War (218-201 bc), Rome was brought to the verge of defeat by the brilliant Carthaginian general, Hannibal, who with his army successfully crossed the supposedly impassable Alps and inflicted three crushing defeats on the Romans in battles in which over 100,000 Romans were killed. Most of the Italians stayed loyal to Rome, however, and drawing on their manpower reserves, the Romans outlasted Hannibal and eventually won the war.
After passing through the crucible of the Second Punic War, Rome's armies were highly professionalized and over the next couple hundred years conquered nearly the entire Mediterranean basin, including the rich, highly cultured world of the Greek East. No longer did Rome share citizenship so freely; instead, these overseas areas were organized as taxpaying provinces. Rome's very overseas success, however, began to create internal tensions as individual generals amassed too much power and prestige, poor Romans lost their farms and fell into debt, the old Italian allies and half-citizens became resentful, and a government system developed to rule a city was strained by having to manage an empire.
These tensions exploded during the Late Republic (133-31 bc), when a sequence of bloody civil wars wracked the Roman world and a succession of ever-more-daring strong men made bids to dominate the state. This process culminated in the civil war between Julius Caesar and Pompey the Great, and after his victory Caesar established himself as dictator for life. His kinglike behavior soon led to his assassination by the senate on the ides of March, 44 bc, and his death touched off a final round of civil wars that ultimately were won by Caesar's adopted son, Octavian, in 31 bc.
Octavian, who was remarkably adept at what would today be considered image making and political propaganda, established himself as the dominant figure in Rome. Now called Augustus, he became the first emperor and ushered in the final era of ancient Roman history, the empire. Despite occasional eccentric or insane emperors such as Nero, the Roman Empire enjoyed relative stability and prosperity for the next 200 years.
In the third century ad, barbarian invasions, economic turmoil, and political instability led to a time of crisis, and complete collapse was only narrowly averted. In ad 312, Constantine became the first emperor to convert to Christianity, and soon after, the empire permanently split into eastern and western halves. The western half staggered along for another century or so but eventually fragmented into numerous barbarian kingdoms. The Eastern (Byzantine) Roman Empire, with its capital at Constantinople, continued to exist for many cenfuries, finally falling to the Ottoman Turks in 1453.