During the time that Macedonians and Greeks conquered the Persian Empire and Hellenistic states spread Greek civilization over large parts of western Asia and Egypt, the Roman Republic subjugated Italy and the western basin of the Mediterranean. In the following centuries, it subdued the eastern half of the Mediterranean as well. The rise of Rome, like the Macedonian and Greek expansion to the east, was ultimately made possible by population increase, especially by the growth of a citizenry that saw in military service both a duty and a right. Roman society was, like Greek society and like the societies of Celts and Germans in “barbaric” Europe, a society in which the full citizen or the free member of the community was a man in possession of arms. In this, as has been stated before, these European cultures differed from most of the more developed states in Asia and Egypt, where the mass of the free population was disarmed. Characteristic of Rome, moreover, was the fact that its political organization rather easily allowed the adoption of outsiders into the Roman community. Whereas defeated peoples could be totally exterminated, which rarely occurred, or be completely enslaved, which occurred more often, they could also, usually after a period of transition of one or a few generations, be incorporated into the Roman citizenry, which in Italy became the rule. That meant by definition an enlargement of the military potential of the Roman people. A Greek polis could rule as a tyrant over other poleis—as democratic Athens had done for some time in the 5th century BC—without adopting the citizens of the latter into her own citizenry. Rome, by contrast, in doing exactly that, could develop into a territorial state in Italy, with an increasing number of Roman towns in its territory. This process had reached a tipping point around 300 BC: since then, none of the other states or peoples in Italy could ever match Rome in military manpower, which made the further subjugation of Italy to Rome a near certainty, unless all the others could permanently unite against her. That did not transpire, and the subjugation of Italy followed in due course during the first decades of the 3rd century BC. With that, Rome could add the manpower of the rest of Italy to her own manpower, which made her at once a formidable power in the wider Mediterranean world. to this reservoir of manpower, Rome could afford to lose big battles and still go on winning the war. All this does not mean that the Roman expansion was somehow an inevitable process, for apart from the means to carry it out—not only in terms of manpower but also an adequate
Military and political organization—there also must have been the will to do so. The will, though, was there in more than sufficient measure. The aristocracy that governed Rome was steeped in a militaristic ethos: fame and prestige were actually only military fame and military prestige, and the career of a successful politician invariably included victories on the battlefield. At the same time, however, the enormous successes of Roman expansion would in the end undermine the foundations of the aristocratic republic itself. For while Rome developed into a large territorial empire, her political organization remained for a long time the organization of a city-state. In the 1st century BC, that organization would finally be overhauled with all the violence of a number of civil wars; those wars would in their turn stimulate further territorial expansion until, in 30 BC, the annexation of the last Hellenistic state would coincide with the end of the republic and the beginning of a new monarchy that seemed more suited to the empire that Rome had by that time become.