The most dangerous enemies of Rome during the reigns of Valerian and Gallienus were the Franks, the Alemanni, and the Goths, whose action finally decided the conquest of the Rhenish provinces of Rome. The name Frank, or Freedman, was given to a confederacy formed in A.D. 240 by the old inhabitants of the Lower Rhine and the Weser. It consisted of the Chauci, the Cherusci, and the Chatti, and of several other tribes of greater or less renown. The Romans foresaw the power of this formidable union and, by the presence of the Emperor himself and his son, endeavoured to stem the invasion, which threatened their suzerainty. The Franks, fond of liberty and imbued with a passion for conquest, crossed the Rhine, in spite of its strong fortifications, and carried their devastations to the foot of the Pyrenees. For twelve years Gallienus attempted to stem the torrent thus freed. The Alemanni, who belonged to the Upper Rhine, between the Main and the Danube, were composed of many tribes, the most important of which was the celebrated Suevi. This people, who had now become a permanent nation, threatened the Empire with an invasion which was checked with difficulty after they had fought their way to the gates of Rome itself. In A.D. 271 Aurelian completely subdued the Rhenish peoples, numbers of whom were dragged in his triumph through the streets of Rome; but after his brief reign the old condition of things reasserted itself, until Probus, who assumed the purple in 276, restored peace and order by the construction of a massive wall between the Rhine and the Danube over two hundred miles in length. The barbarians were driven beyond the river, which had hitherto served as a boundary-line, even past the Elbe and the Neckar. Finally, however, the internecine strife in the Imperial City forced the Romans to return thence, and Rhineland was abandoned to the will of its semi-barbarian inhabitants. The early Christian centuries are full of the sound of conflict. In the fourth century the principal tribes in Western Germany were the Franks and the Alemanni, the former of whom maintained a constant strife with the Saxons, who pressed heavily upon their rear. The Franks occupied the lower portion of the river, near to its mouth, whilst the Alemanni dwelt on the portion to the bounds of Helvetia and Switzerland. At this period great racial upheavals appear to have been taking place further east. By the beginning of the sixth century the Saxons seem to have penetrated almost to the north-western Rhine, where the Franks were now supreme. The Merovingians