The upper Germanic Limes.We cannot historically follow out the mode in which the frontier–fence between the Rhine and the Danube—still in great part subsisting as regards its foundations at the present day—came into existence, but we are able to recognise not merely the course which it took but also the purpose which it served. The work was as to its nature and purpose different in upper Germany from what it was in Raetia. The upper German frontier–fence, with a length in all of about 250 Roman miles (228 English miles[82]) begins immediately at the northern boundary of the province, embraces, as has been already said, the Taunus and the plain of the Main as far as the district of Friedberg, and turns thence southward to the Main, which it meets at Grosskrotzenburg above Hanau. Following the Main thence as far as Wörth, it here takes the direction of the Neckar, which it reaches somewhat below Wimpfen and does not again leave. Afterwards in front of the southern half of this frontier–line a second was laid out, which follows the Main by way of Wörth as far as Miltenberg, and thence is led for the most part in a straight direction to Lorch between Stuttgart and Aalen. Here to the upper German frontier–fence is joined on the Raetian, only 120 miles (108 English) long; it leaves the Danube at Kelheim above Ratisbon and runs thence, twice crossing the Altmuhl, in a curve westward likewise as far as Lorch.
The upper Germanic Limes consists of a series of forts which are distant from each other, at the most, half a day’s march (about nine English miles). Where the lines of connection between the forts are not closed by the Main or the Neckar, as stated above, there was introduced an artificial barrier, at first perhaps merely by a palisade,[83] afterwards by a continuous earthen rampart of moderate height, with a fosse outside and watch–towers built in at short intervals on the inner side.[84] The forts are not introduced into the rampart, but constructed immediately behind it at a distance seldom exceeding one–third of an English mile.
The Raetian Limes.The Raetian frontier–fence was a mere barrier, produced by piling up quarry–stones; there were no fosses or watch–towers, and the forts, constructed behind the Limes without regular succession and at unequal intervals (none nearer than two and a half to three miles), stand in no immediate connection with the barrier–line. As to the order in time of the constructions there is no definite testimony; it is proved that the upper Germanic line of the Neckar was in existence under Pius,[85] that placed in front of it from Miltenberg to Lorch under Marcus.[86] The idea of a frontier–bar was common to the two structures, otherwise so different; the preference in the one case for the piling up of earth—whence the fosse for the most part resulted of itself—in the other case, for layers of stone, probably depended only on the diversity of the soil and of the materials for building. It was common to them, further, that neither the one nor the other was constructed for the defence, as a whole, of the frontier. Not merely was the hindrance, which the piling up of earth or stone presented to the assailant, slight in itself; but along the line we meet everywhere with commanding positions, morasses lying in the rear, a want of outlook towards the country in front, and similar clear indications of the fact, that in the tracing of it warlike purposes generally were not contemplated. The forts are of course arranged for defence, each by itself, but they are not connected by paved cross–roads; and so the individual garrison relied for support not on those of the neighbouring forts, but on the rear–base, to which the road led, whereby each was kept garrisoned. Moreover, these garrisons were not dovetailed into a military system of frontier defence; they were rather fortified positions for a case of need than strategically chosen for the occupation of the territory, as indeed the very extent of the line itself, compared with the number of troops at disposal, excludes the possibility of its defence as a whole.[87]
Object of these structures.Thus these extensive military structures had not, like the Britannic wall, the object of checking the invasion of the enemy. The intention rather was, that, like the bridges over the river–frontier, so the roads on the land–frontier should be commanded by the forts, but in other respects, like the river as the water–boundary, so the wall on the landward should hinder the uncontrolled crossing of the frontier. Other uses might be combined with this; the preference, often apparent, for the rectilineal direction points to its application for signals, and occasionally the structure may have been used directly for purposes of war. But the proper and immediate object of the structure was to prevent the crossing of the frontier. The fact, withal, that watch–posts and forts were erected, not on the Raetian but on the upper Germanic frontier, is explained by their different relations to the neighbours, in the former case to the Hermunduri, in the latter to the Chatti. The Romans in upper Germany did not confront their neighbours as they confronted the Highlanders of Britain, in whose presence the province was always in a state of siege; but the repulse of predatory invaders as well as the levying of the frontier–dues demanded at any rate ready and near military help. The upper German army, and in keeping with it the garrisons on the Limes, might be gradually reduced, but the Roman pilum could never be dispensed with in the land of the Neckar. It might, however, be dispensed with in presence of the Hermunduri, who, in Trajan’s time, alone of all the Germans, were at liberty to cross the frontier of the empire without special control and to trade freely in the Roman territory, especially in Augsburg, and with whom, so far as we know, border–collisions never took place. There was thus at this period no occasion for a similar structure on the Raetian frontier; the forts north of the Danube, which can be shown to have subsisted already in Trajan’s time,[88] sufficed here for the protection of the frontier and the control of frontier–intercourse. This accords with the observation that the Raetian Limes, as it stands before our eyes, corresponds only with the more recent upper Germanic barrier–line perhaps laid out for the first time under Marcus. Then occasion for it was not wanting. The wars of the Chatti, as we shall see ([p. 161]), seized at this time also on Raetia; the strengthening too of the garrison of the province might reasonably stand in connection with the erection of this Limes, which, however little it was arranged for military ends, was at any rate doubtless constructed with a view to its being a frontier–bar, though of less strong character.[89]
Their effect.In a military as well as a political sense the shifting of the frontier, or rather the strengthening of the frontier–fence, was effective and useful. While formerly the Roman chain of forts in upper Germany and Raetia probably went up the Rhine by way of Strassburg to Basel and along by Vindonissa to the lake of Constance, then from thence to the upper Danube, now the upper German headquarters were in Mentz and the Raetian in Ratisbon, and generally the two chief armies of the empire were brought considerably nearer to each other. The legionary camp of Vindonissa (Windisch near Zürich) became thereby superfluous. The army of the upper Rhine could, like the neighbouring one, be reduced after some time to the half of its former strength. The original number of four legions, which was only accidentally diminished to three during the Batavian war, subsisted, at all events, probably still under Trajan;[90] but under Marcus the province was only occupied by two legions, the 8th and the 22d, of which the former was stationed at Strassburg, the second at the headquarters Mentz, while most of the troops, broken up into smaller posts, were stationed along the frontier–wall. Within the new line urban life flourished almost as on the left bank of the Rhine; Sumelocenna (Rottenburg on the Neckar), Aquae (civitas Aurelia Aquensis, Baden), Lopodunum (Ladenburg), had, if we except Cologne and Treves, to fear no comparison as respects Roman urban development with any town of Belgica. The rise of these settlements was chiefly the work of Trajan, who began his government with this act of peace;[91] “the Rhine Roman on both its banks” is what a Roman poet entreats speedily to send to Rome its yet unseen ruler. The great and fertile region, which was placed in this way under the protection of the legions, needed that protection and was worthy of it. Doubtless the battle of Varus marks the beginning of the ebb of Roman power, but only in so far as its advance was thereby ended, and the Romans thenceforth contented themselves in general with shielding more vigorously and continuously what was retained.
Germany under Marcus.Down to the beginning of the third century the Roman power on the Rhine showed no indications of tottering. During the war with the Marcomani under Marcus all remained quiet in the lower province. If a legate of Belgica had at that time to call out the general levy against the Chauci, this was presumably a piratical expedition, such as often visited the north coast at this time, just as earlier and later. The surge of the great movement of peoples reached to the sources of the Danube and even as far as the region of the Rhine; but it did not shake the foundations there. The Chatti, the only considerable Germanic tribe on the upper German and Raetian border–fence, pushed forward in both directions, and were probably at that time even among the Germans invading Italy, as will be shown further on when we describe this war. At any rate the reinforcement of the Raetian army at that time ordained by Marcus, and its conversion into a command of the first class with legion and legates, can only have taken place in order to check the attacks of the Chatti, and proves that they did not treat them lightly as regards the future. The already–mentioned strengthening of the border–defence would likewise stand connected with this movement. These measures must have sufficed for the next generation.
War with the Alamanni.Under Antoninus the son of Severus a new and more severe war once more (213) broke out in Raetia. This also was waged against the Chatti; but by their side a second people is named, which we here meet for the first time—the Alamanni. Whence they came, we know not. According to a Roman writing a little later they were a conflux of mixed elements; the appellation also seems to point to a league of communities, as well as the fact that afterwards the different tribes comprehended under this name stand forth—more than is the case among the other great Germanic peoples—in their separate character, and the Juthungi, the Lentienses, and other Alamannic peoples not seldom act independently. But that it is not the Germans of this region who here emerge allied under the new name and strengthened by the alliance, is shown as well by the naming of the Alamanni alongside of the Chatti, as by the mention of the unwonted skilfulness of the Alamanni in equestrian combat. On the contrary it was certainly, in the main, hordes coming on from the East that lent new strength to the almost extinguished German resistance on the Rhine; it is not improbable that the powerful Semnones, in earlier times dwelling on the middle Elbe, of whom there is no further mention after the end of the second century, furnished a strong contingent to the Alamanni.Severus Antoninus. The constantly increasing misgovernment in the Roman empire naturally contributed its share, although only in a secondary degree, to the shifting of power. The emperor took the field in person against the new foe; in August of the year 213 he crossed the Roman frontier, and a victory over them on the Main was achieved or at least celebrated; further forts were constructed; the tribes of the Elbe and of the North Sea sent deputies to the Roman ruler, and wondered when in receiving them he wore their own dress, with silver–mounted jacket, and hair and beard coloured and arranged after the German fashion. But thenceforth the wars on the Rhine are incessant, and the aggressors are the Germans; the neighbours formerly so pliant had as it were exchanged characters. Twenty years later the inroads of the barbarians on the Danube as on the Rhine were so constant and so serious, Alexander.that the emperor Alexander had on their account to break off the less immediately dangerous Persian war and to resort in person to the camp of Mentz, not so much to defend the territory as to purchase peace from the Germans by large sums of money. The exasperation of the soldiers at this led to his murder (A.D. 235), and thereby to the fall of the Severian dynasty, the last that existed at all until the regeneration of the state.