In its initial days Rome was a monarchy, but over the course of time people tired of having a single man rule them until death and so the kingdom became a republic and had a semblance of democratic rule. From 500 to 50 BC, Rome had remained a republic with elected representation at least from the elite patricians (the ruling classes).
However, Hannibal’s war (The Punic Wars) had laid waste to the roman countryside and many people had made their way to the city; this led to a large plebeian population and slave rebellions, especially from gladiators (slaves trained to fight to the death, who had nothing to lose). The increasing population of Plebeians who did not have the hereditary rights of the patriarchs led to the steady erosion of the political power of the Roman republic. This, in turn meant that generals became more powerful and they could command the political class to do their bidding.
Eventually it culminated in the rise of Julius Caesar and after his murder by the Roman Senate (popularized as the ides of March) his adopted nephew Octavian swept away the old republic and became the First Emperor Augustus. This led to Pax Romana or “Roman Peace” as Rome reached the very zenith of her power and reach.
However, with the passage of time the Imperial class became decadent and allowed rulers such as Caligula and Nero to take over the reins of power. Of the latter, it has been said that he was the most inefficient ruler to sit on a throne, at any time in history. While the Roman Empire had outlasted such megalomaniacs (Caligula had once ordered the mighty legions to attack the sea and take the shells as ‘war booty’), it became weaker as corruption and luxury became the order of the day.
The famed ‘Eagles’, as the mighty legions of Rome were called, had their training shortened from a five year period to a few months at most. Once Rome lost the tip of her spear, her decadence and downward spiral was inevitable. The riches ultimately attracted barbarians.
When Attila the Hun attacked there was little the Romans could do against this most merciless of warriors. In perhaps their last hurrah, Rome gathered all her strength and met this destroyer of nations in open battle where he was defeated, in much the same way his predecessor Hannibal was defeated, centuries before. Once again, Roman velour and tactics had triumphed. However, this time Rome had nothing left to go on. And shortly afterward, the invading barbarians started taking over territory after territory and the city was eventually sacked, plundered and abandoned.
But at the height of its power, Rome had been divided into two parts by emperor Byzantine. The Western Roman Empire was ruled from Rome proper and the eastern one, by the city of Byzantium. And while the city of Rome faded into oblivion its military, social and political traditions were carried on by the newly resurgent Byzantine empire, the successor to the original Rome.