*Valerian and Gallienus: 253–268 A. D.* The fortunes of the Empire reached their lowest ebb under Valerian and his son Gallienus (253–268 A. D.). In 256, the Persians invaded Mesopotamia and Syria, and captured Antioch. Valerian at once undertook the defence of the eastern provinces, leaving Gallienus in charge of the West. Antioch was recovered, but when Valerian entered Mesopotamia to relieve the blockade of Edessa, he was defeated by the Persian king Sapor, and taken prisoner (258 A. D.). He died soon afterwards in captivity. The Persians not only reoccupied Antioch but also seized Tarsus in Cilicia and Caesarea in Cappadocia, and ravaged Asia Minor to the shores of the Aegean Sea. While Valerian was waging his ill-fated war in the East, the rest of the empire was in a continual state of turmoil. In 257 the Goths and other peoples overran Dacia, crossed the Danube and penetrated as far south as Macedonia and Achaia. In 258 a revolt broke out in Mauretania. The Berber tribesmen, led by an able chief, Faraxen, invaded the province of Numidia, and were only reduced to submission by the capture of their leader (260 A. D.). At the same time the Alamanni broke into Raetia, and made their way over the Alps into the Po valley. Gallienus hastened to the rescue and defeated them near Milan. But in his absence in Italy the Franks crossed the Rhine and poured in devastating hordes over Gaul and Spain. The Roman possessions on the right bank of the Rhine were lost at this time and never recovered. *The empire of the Gauls.* At the news of the death of Valerian the commander in Pannonia, Ingenuus, raised the standard of revolt. After defeating him, Gallienus found another serious rival in Regalianus, whom, however, he was likewise able to overcome. But at the same time (258 A. D.), Marcus Cassius Latinius Postumus, whom Gallienus had left in command in Gaul, assumed the imperial title, after a victory gained over a body of Franks. He was able to clear Gaul of its foes and make himself master of Britain and Spain. Gallienus was powerless to depose him. Postumus did not endeavor to establish a national Gallic state but regarded himself as exercising the Roman _imperium_ in a portion of the empire. He fixed his capital at Trèves, and organized a senate and other institutions on the Roman model. His coins bore the inscription _Roma Aeterna_.