One of Hanson's claims as to the distinctive way of Western war regards its voluntary inclusiveness - all citizens fought and fought more or less voluntarily. Yes, institutions mattered, technology mattered, military tactics mattered, but one of the key distinctions was free citizens choosing to fight. I'll come back to that argument later, but one of the constraints on the size of an army in such a system is the number of citizens. Sparta, famously, declined as a military power, not so much because their exceptional soldiers became slack but because they ran out of Spartans.
Hanson explores how the idea of citizenry changed under the Romans in a fashion that helped address the constraint that the number of citizens placed on the size of the army.
This revolutionary idea of Western citizenship - replete with ever more rights and responsibilities - would provide superb manpower for the growing legions and a legal framework that would guarantee that the men who fought felt that they themselves in a formal and contractual sense had ratified the conditions of their own battle service. The ancient Western world would soon come to define itself by culture rather than by race, skin color, or language. That idea alone would eventually bring enormous advantages to its armies on the battlefield. In the centuries of empire to follow, the legionaries of a frontier garrison in northern England, or northern Africa would look and speak differently from the men who died at Cannae. They would on occasion experience cultural prejudice from native Italians; nevertheless, they would also be equipped and organized in the same fashion as traditional Roman soldiers, and as citizens they would see their military service as a contractual agreement rather than ad hoc impressment.I am currently also reading War! What Is It Good For? by Ian Morris. In it, he argues that war, while tragically destructive, has also exerted positive influences in the development of ideas, institutions, technology, etc. This example where the manpower needs for effective war fighting and its effect as a driving force towards an expansive definition of citizenship beyond race, ethnicity, religion, class, etc. would seem to be an example that supports his thesis.
Even as early as the Punic Wars slaves in real numbers were on occasion freed and, depending on their military contribution, given Roman citizenship. The aftermath of Cannae would see their military participation and emancipation in the thousands. The Romans, in short, had taken the idea of a polis and turned it into the concept of natio: Romanness would soon not be defined concretely and forever by race, geography, or even free birth. Rather, citizenship in theory could be acquired someday by those who did not speak Latin, who were born even into servitude, and who lived outside Italy — if they could convince the relevant deliberative bodies that they were Roman in spirit and possessed a willingness to take on Roman military service and pay taxes in exchange for the protection of Roman law and security brought on by a free and mercantile economy.
Juvenal three centuries after Cannae would ridicule the "hungry Greeklings" that bustled about Rome, but such men ran the commercial life of Rome and would prove to be, along with thousands of other foreigners like them, as good citizen legionaries as any Italians. Rome, not classical Greece, created the modern expansive idea of Western citizenship and the notion of plutocratic values that thrive in a growing and free economy. Money, not necessarily birth, ancestry, or occupation, would soon bring a Roman status. The ex-slave Trimalchio and his nouveau riche freedmen dinner guests, lounging in splendor in Petronius's first-century-A.D. novel, the Satyricon, were the logical fruit of the entire Roman evolution in civic inclusiveness - social, economic, and cultural - that went on even as political liberty at the national level was further extinguished under the empire. It is no accident that some of the most Roman and chauvinistic of Latin authors - Terence, Horace, Publius Syrus, Polybius, and Josephus - were themselves the children of freedmen, ex-slaves, Africans, Asians, Greeks, or Jews. By the second century A.D. it was not common to find a Roman emperor who had been born at Rome. What effect did this vast difference in the respective ideas of citizenship of the antagonists have on the fighting in August 216 B.C.? Quite a lot - very few trained mercenary replacements available to Hannibal in the exuberance of victory, a multitude of raw militiamen recruits for Rome in the dejection of defeat.
The earlier Greeks had invented the idea of civic militarism, the notion that those who vote must also fight to protect the commonwealth, which in the exchange had granted them rights. The result was that the classical city-states came to field infantries made up of almost half their male resident population. At the battle of Plataea (479 s.c.) perhaps 70,000 free Greek citizens annihilated a Persian army of 250,000 forced conscripts. This was a good start in mobilizing the manpower reserves of the tiny Hellenic landed republics well beyond the old aristocratic elite. Nevertheless, the potential of civic militarism was never fully appreciated by the classical Greeks due to their jealously guarded notion of citizenship that was not extended to all residents of the polis. The Greeks had kept Hellas free from Persian occupation in part through the revolutionary idea that all the citizens must serve in the battle, but by the same token lost their autonomy a century and a half later to the Macedonians through a shortage of just those citizen warriors.
The solution to this classical paradox was to field spirited citizen armies that were nevertheless huge, combining the classical Greek discovery of civic militarism with the Hellenistic dynasts' willingness to recruit infantrymen from all segments of society. The Roman nation and its radical idea of an expansive citizenship would eventually do both brilliantly — in the process ensuring that its armies were larger than those of the classical Greeks and yet far more patriotic than the mercenaries who enrolled in the thousands in service to the Hellenistic monarchs.
In fact, I think the Western tradition of increasing inclusiveness is a root characteristic of its development. Not only does inclusiveness increase the capacity for defense (and offense) but productivity as well. If women are precluded from the formal workforce, your productivity is sharply curtailed. If people, regardless of their capabilities, are constrained to hereditary functions or classes, your productivity is curtailed. If people of different religions are constrained from what roles in the economy they are allowed to play, your productivity is constrained.
Under this telling - the Western tradition of tolerance and inclusion (whether exercised through goodwill or necessity) becomes a distinguishing characteristic, militarily and economically, from other traditions.