The camp of a Roman legion presented the appearance of a fortified city. 60 As soon as the space was marked out, the pioneers carefully levelled the ground, and removed every impediment that might interrupt its perfect regularity. Its form was an exact quadrangle; and we may calculate, that a square of about seven hundred yards was sufficient for the encampment of twenty thousand Romans; though a similar number of our own troops would expose to the enemy a front of more than treble that extent. In the midst of the camp, the praetorium, or general’s quarters, rose above the others; the cavalry, the infantry, and the auxiliaries occupied their respective stations; the streets were broad and perfectly straight, and a vacant space of two hundred feet was left on all sides between the tents and the rampart. The rampart itself was usually twelve feet high, armed with a line of strong and intricate palisades, and defended by a ditch of twelve feet in depth as well as in breadth. This important labor was performed by the hands of the legionaries themselves; to whom the use of the spade and the pickaxe was no less familiar than that of the sword or pilum. Active valor may often be the present of nature; but such patient diligence can be the fruit only of habit and discipline.61
Whenever the trumpet gave the signal of departure, the camp was almost instantly broke up, and the troops fell into their ranks without delay or confusion. Besides their arms, which the legendaries scarcely considered as an encumbrance, they were laden with their kitchen furniture, the instruments of fortification, and the provision of many days. 45 Under this weight, which would oppress the delicacy of a modern soldier, they were trained by a regular step to advance, in about six hours, near twenty miles. 63 On the appearance of an enemy, they threw aside their baggage, and by easy and rapid evolutions converted the column of march into an order of battle. 64 The slingers and archers skirmished in the front; the auxiliaries formed the first line, and were seconded or sustained by the strength of the legions; the cavalry covered the flanks, and the military engines were placed in the rear.
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 Rhaetia, one in Noricum, four in Pannonia, three in Maesia, 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 Praetorian Guards, watched over the safety of the monarch and the capital. As the authors of almost every revolution that distracted the empire, the Praetorians 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. 65
The navy maintained by the emperors might seem inadequate to their greatness; but it was fully sufficient for every useful purpose of government. The ambition of the Romans was confined to the land; nor was that warlike people ever actuated by the enterprising spirit which had prompted the navigators of Tyre, of Carthage, and even of Marseilles, to enlarge the bounds of the world, and to explore the most remote coasts of the ocean. To the Romans the ocean remained an object of terror rather than of curiosity; 66 the whole extent of the Mediterranean, after the destruction of Carthage, and the extirpation of the pirates, was included within their provinces. The policy of the emperors was directed only to preserve the peaceful dominion of that sea, and to protect the commerce of their subjects. With these moderate views, Augustus stationed two permanent fleets in the most convenient ports of Italy, the one at Ravenna, on the Adriatic, the other at Misenum, in the Bay of Naples. Experience seems at length to have convinced the ancients, that as soon as their galleys exceeded two, or at the most three ranks of oars, they were suited rather for vain pomp than for real service. Augustus himself, in the victory of Actium, had seen the superiority of his own light frigates (they were called Liburnians) over the lofty but unwieldy castles of his rival. 67 Of these Liburnians he composed the two fleets of Ravenna and Misenum, destined to command, the one the eastern, the other the western division of the Mediterranean; and to each of the squadrons he attached a body of several thousand marines. Besides these two ports, which may be considered as the principal seats of the Roman navy, a very considerable force was stationed at Frejus, on the coast of Provence, and the Euxine was guarded by forty ships, and three thousand soldiers. To all these we add the fleet which preserved the communication between Gaul and Britain, and a great number of vessels constantly maintained on the Rhine and Danube, to harass the country, or to intercept the passage of the barbarians. 68If we review this general state of the Imperial forces; of the cavalry as well as infantry; of the legions, the auxiliaries, the guards, and the navy; the most liberal computation will not allow us to fix the entire establishment by sea and by land at more than four hundred and fifty thousand men: a military power, which, however formidable it may seem, was equalled by a monarch of the last century, whose kingdom was confined within a single province of the Roman empire. 69