Such were the arts of war, by which the Roman emperors defended their extensive conquests, and preserved a military spirit, at a time when every other virtue was oppressed by luxury and despotism. If, in the consideration of their armies, we pass from their discipline to their numbers, we shall not find it easy to define them with any tolerable accuracy. We may compute, however, that the legion, which was itself a body of six thousand eight hundred and thirty-one Romans, might, with its attendant auxiliaries, amount to about twelve thousand five hundred men. The peace establishment of Hadrian and his successors was composed of no less than thirty of these formidable brigades; and most probably formed a standing force of three hundred and seventy-five thousand men. Instead of being confined within the walls of fortified cities, which the Romans considered as the refuge of weakness or pusillanimity, the legions were encamped on the banks of the great rivers, and along the frontiers of the barbarians. As their stations, for the most part, remained fixed and permanent, we may venture to describe the distribution of the troops. Three legions were sufficient for Britain. The principal strength lay upon the Rhine and Danube, and consisted of sixteen legions, in the following proportions: two in the Lower, and three in the Upper Germany; one in Rhætia, one in Noricum, four in Pannonia, three in Mæsia, and two in Dacia. The defence of the Euphrates was intrusted to eight legions, six of whom were planted in Syria, and the other two in Cappadocia. With regard to Egypt, Africa, and Spain, as they were far removed from any important scene of war, a single legion maintained the domestic tranquillity of each of those great provinces. Even Italy was not left destitute of a military force. Above twenty thousand chosen soldiers, distinguished by the titles of City Cohorts and Prætorian Guards, watched over the safety of the monarch and the capital. As the authors of almost every revolution that distracted the empire, the Prætorians will, very soon, and very loudly, demand our attention; but, in their arms and institutions, we cannot find any circumstance which discriminated them from the legions, unless it were a more splendid appearance, and a less rigid discipline.