Each of these four levy-districts had to furnish approximately the fourth part not only of the force as a whole, but of each of its military subdivisions, so that each legion and each century numbered an equal proportion of conscripts from each region, in order to merge all distinctions of a gentile and local nature in the one common levy of the community and, especially through the powerful levelling influence of the military spirit, to blend the metoeci and the burgesses into one people.
In a military point of view, the male population capable of bearing arms was divided into a first and second levy, the former of which, the "juniors" from the commencement of the eighteenth to the completion of the forty-sixth year, were especially employed for service in the field, while the "seniors" guarded the walls at home. The military unit came to be in the infantry the now doubled legion[9] - a phalanx, arranged and armed completely in the old Doric style, of 6000 men who, six file deep, formed a front of 1000 heavy-armed soldiers; to which were attached 2400 "unarmed"[10]. The four first ranks of the phalanx, the classis, were formed by the fully-armed hoplites of those possessing a full hide; in the fifth and sixth were placed the less completely equipped farmers of the second and third division; the two last divisions were annexed as rear ranks to the phalanx or fought by its side as light-armed troops. Provision was made for readily supplying the accidental gaps which were so injurious to the phalanx. Thus there served in it 84 centuries or 8400 men, of whom 6000 were hoplites, 4000 of the first division, 1000 from each of the two following, and 2400 light-armed, of whom 1000 belonged to the fourth, and 1200 to the fifth division; approximately each levy-district furnished to the phalanx 2100, and to each century 25 men. This phalanx was the army destined for the field, while a like force of troops was reckoned for the seniors who remained behind to defend the city. In this way the normal amount of the infantry came to 16,800 men, 80 centuries of the first division, 20 from each of the three following, and 28 from the last division--not taking into account the two centuries of substitutes or those of the workmen or the musicians. To all these fell to be added the cavalry, which consisted of 1800 horse; often when the army took the field, however, only the third part of the whole number was attached to it. The normal amount of the Roman army of the first and second levy rose accordingly to close upon 20,000 men: which number must beyond doubt have corresponded on the whole to the effective strength of the Roman population capable of arms, as it stood at the time when this new organization was introduced. As the population increased the number of centuries was not augmented, but the several divisions were strengthened by persons added, without altogether losing sight, however, of the fundamental number. Indeed the Roman corporations in general, closed as to numbers, very frequently evaded the limit imposed upon them by admitting supernumerary members.
This new organization of the army was accompanied by a more careful supervision of landed property on the part of the state. It was now either ordained for the first time or, if not, at any rate defined more carefully, that a land-register should be established, in which the several proprietors of land should have their fields with all their appurtenances, servitudes, slaves, beasts of draught and of burden, duly recorded. Every act of alienation, which did not take place publicly and before witnesses, was declared null; and a revision of the register of landed property, which was at the same time the levy-roll, was directed to be made every fourth year. The mancipatio and the census thus arose out of the Servian military organization.
It is evident at a glance that this whole institution was from the outset of a military nature. In the whole detailed scheme we do not encounter a single feature suggestive of any destination of the centuries to other than purely military purposes; and this alone must, with every one accustomed to consider such matters, form a sufficient reason for pronouncing its application to political objects a later innovation. If, as is probable, in the earliest period every one who had passed his sixtieth year was excluded from the centuries, this has no meaning, so far as they were intended from the first to form a representation of the burgess-community similar to and parallel with the curies. Although, however, the organization of the centuries was introduced merely to enlarge the military resources of the burgesses by the inclusion of the metoeci and, in so far, there is no greater error than to exhibit the Servian organization as the introduction of a timocracy in Rome - yet the new obligation imposed upon the inhabitants to bear arms exercised in its consequences a material influence on their political position. He who is obliged to become a soldier must also, so long as the state is not rotten, have it in his power to become an officer; beyond question plebeians also could now be nominated in Rome as centurions and as military tribunes. Although, moreover, the institution of the centuries was not intended to curtail the political privileges exclusively possessed by the burgesses as hitherto represented in the curies, yet it was inevitable that those rights, which the burgesses hitherto had exercised not as the assembly of curies, but as the burgess-levy, should pass over to the new centuries of burgesses and metoeci. Henceforward, accordingly, it was the centuries whose consent the king had to ask before beginning an aggressive war[11]. It is important, on account of the subsequent course of development, to note these first steps towards the centuries taking part in public affairs; but the centuries came to acquire such rights at first more in the way of natural sequence than of direct design, and subsequently to the Servian reform, as before, the assembly of the curies was regarded as the proper burgess-community, whose homage bound the whole people in allegiance to the king. By the side of these new landowning full-burgesses stood the domiciled foreigners from the allied Latium, as participating in the public burdens, tribute and task-works (hence municipes); while the burgesses not domiciled, who were beyond the pale of the tribes, and had not the right to serve in war and vote, came into view only as "owing tribute" (aerarii).