The legions came to be distinguished by numbers, indicating the order of enlistment in the eastern or western division of the empire respectively, or by special designations of honour, such as the martia, or the victrix. With their names or numbers the particular history of each was duly recorded, and some of them became noted perhaps for a peculiar character and physiognomy of their own. The principle of permanence thus established to his hand, Augustus carried it out systematically, and extended it from the provinces to Rome itself. He instituted a special service for the protection of his own person, in imitation of the select battalion which kept watch round the imperator’s tent. These prætorian guards were gratified with double pay, amounting to two denarii daily, and the prospect of discharge at the end of twelve years, while the term of service for the legionaries was fixed at sixteen. They were recruited from Latium, Etruria, Umbria, and the old Roman colonies of central Italy exclusively. They were regarded accordingly as a force peculiarly national, nor when reminded of this distinction were they insensible of the compliment. But the emperor did not entrust his security to these Italian troops only. Besides the prætorian cohorts he kept about his person a corps of picked veterans from the legions, a few hundred in number, together with a battalion of German foot soldiers and a squadron of Batavian horse. Cæsar had employed these barbarians, distinguished for their personal strength and courage, on the wings of his own armies, and his successor may have placed this confidence in them on account of their tried fidelity. In addition, however, to these household troops, the whole number of which did not exceed five or six thousand, Augustus first introduced a regular garrison into the city, consisting of four cohorts of fifteen hundred men each, which were also levied exclusively in Italy. He established no permanent camp or fortress to overawe the capital. The soldiers were billeted on the inhabitants or lodged in the public edifices; they were always at hand to repress tumults and preserve the peace of the city, when the stores of grain ran low and the prevalence of tempests on the coast menaced it with prolonged scarcity. But the ordinary police of the streets was maintained by an urban guard, named _vigiles_ or the watch, seven hundred of whom sufficed for the service. The whole armed force of every description employed in the city might amount to twelve or fifteen thousand men.