The strength of the phalanx depended on sixteen ranks of long pikes, wedged together in the closest array.

But it was soon discovered by reflection, as well as by the event, that the strength of the phalanx was unable to contend with the activity of the legion.
The cavalry, without which the force of the legion would have remained imperfect, was divided into ten troops or squadrons; the first, as the companion of the first cohort, consisted of a hundred and thirty-two men; whilst each of the other nine amounted only to sixty-six.

The entire establishment formed a regiment, if we may use the modern expression, of seven hundred and twenty-six horse, naturally connected with its respective legion, but occasionally separated to act in the line, and to compose a part of the wings of the army.

The cavalry of the emperors was no longer composed, like that of the ancient republic, of the noblest youths of Rome and Italy, who, by performing their military service on horseback, prepared themselves for the offices of senator and consul; and solicited, by deeds of valor, the future suffrages of their countrymen.

Since the alteration of manners and government, the most wealthy of the equestrian order were engaged in the administration of justice, and of the revenue; and whenever they embraced the profession of arms, they were immediately intrusted with a troop of horse, or a cohort of foot.