At the beginning of the Third Century A.D. the work of Augustus and others was beginning to fall to pieces; in the Fourth, it was scarcely anywhere in evidence, and by the end of the Fifth it had become a thing of the past. The exi gencies of herder warfare, with the extended system of permanent camps connected by pa trols, had developed cavalry and light infantry at the expense of the older legion. In the Third Century A.D. the elaborate system of fron tier defense and interior garrisons broke down, and the Empire was subjected to both civil war and foreign invasion. While the legions were engaged in civil strife, the opportunity of the enemy arrived. The frontiers were simultane ously attacked, and the Empire reeled under the shock. The Persians were rising to power in the East (A.D. 220) ; the German tribes were confederating and becoming correspondingly formidable; and the Franks, Alemanni, and Goths appeared along the Rhine and the Dan ube. Diocletian, however, with the reconquest of Britain in A.D. 297, restored the Empire to a semblance of its former power and unity. With the aid of wholesale taxation he replen ished the exchequer, and regarrisoned the mili tary frontier. The changes and additions brought about by Diocletian are remarkable for the value he placed on the troops of mixed nationality and for the growing neglect of the an cient Roman legion. Re also enlisted many new bodies of horsemen; condi. ala-, resilla tiones, etc., being raised alike for. the limitary,
the eomitatensian, and the Palatine armies, among whom Germans. _Moors, and Persians were more numerous than the born subjects of the Empire. Under Constantine, the old legion ary cavalry disappeared altogether, and cavalry and infantry became separate commands; yet under him and his successors, though cavalry grew considerably in relative importance, the infantry still remained the more important arm. The decadence in physique and morale of the Roman army at this time was largely due to the fact that the corps were less homo geneous, and the substitutes and recruits bought by the land-holding classes were often of bad material. The increasing boldness of their foes and the constant civil and internal dissensions had a baleful effect on the old-time csprit-de corps of the rank and file, and, together with the growing luxury and increasingly enervating vice of the times, soon brought about the dis integration and decay of the magnificent Em pire. It is interesting to note that in many instances modern conditions have compelled the adoption of units of military command and forms of military procedure strikingly similar to those of the Romans; while the legionaries' sword, after passing through the radical forms and changes of the Middle Ages, has again ap peared in the shape of the modern infantfy sword-bayonet, which in shape and size closely resembles the Roman sword.