regular duty in making up the required number.[560] Service equo privato could also be imposed as a punishment. The only known instance, however, was that required by the censors of 209 of the equites who had disgraced themselves at Cannae. Their horses were taken from them, their campaigns equo publico were not counted to their credit, but they were required to serve ten years equis privatis.[561] These are the only instances of service with private horses mentioned in history. In all ancient literature is no suggestion that the equites equo privato formed a rank by themselves or were an institution.[562] It should also be said that the injustice of furnishing some with horses and of compelling others to go to war at their own expense, unless by way of punishment, was contrary to the spirit of the constitution. This conclusion is supported by the elder Pliny’s[563] definition of the military equites, which makes the public horse an essential. From the time therefore when the state began to support the mounted service in the way described above, the equites equis publicis continued to be the only regular citizen horsemen. The number of equites with public horses is approximately determined for any time by the number of legions then enrolled. The Servian phalanx, as has been noted,[564] consisted of two legions, which remained the normal number through the fifth century. But in the wars with Samnium and Pyrrhus Rome was able regularly to support four legions.[565] The military force could not have been doubled before the incorporation of the Veientan territory early in the fourth century;[566] most probably the enlargement belongs to still later time. The increase in the infantry required a corresponding enlargement of the mounted service. At least twelve hundred equites were henceforth required for active duty. Making allowance for reserves and ineffectives, the government raised the number of equites equo publico to eighteen hundred. The twelve new centuries were open alike to patricians and plebeians, whereas the old six remained for a time exclusively patrician. This seems to have been the condition at the opening of the first war with Carthage. During the Punic wars the number varied greatly, sometimes reaching a total of more than five thousand in the field, not counting reserves.[567] After the war with Hannibal the state, drained of men and money, allowed the cavalry to dwindle.[568] Viewing this condition with alarm, the elder Cato[569] urged that the number should be increased, and that a minimal limit be fixed at 2200. Probably at the same time he proposed that the legion should be strengthened. His measure must have been adopted, for after his censorship we find the legion regularly consisting of 5200 foot and 300 horse.[570] Under Augustus there were times when 5000 equites[571] equo publico took part in the parade which he revived.[572] As no reason can be found why Augustus should suddenly increase this