where the barbarians were kept at bay, while Gaul was overrun by the Franks, Rhaetia by the Alemans, Thrace and the Mediterranean by the Goths, and the east by Shapur I. Probus became amongst the highest placed lieutenants of Aurelian, reconquering Egypt from Zenobia in 273 A.D. Emperor Tacitus, upon his accession in 275, appointed Probus supreme chief of the east, granting him extraordinary powers in order to secure a dangerous frontier. Though the details are not specified, he is said to have fought with success on almost every frontier of the empire, before his election as emperor by the troops upon Tacitus' death in 276, in his camp in Asia Minor. As emperor Florian, the half-brother of Tacitus, also proclaimed himself emperor, and took control of Tacitus' army in Asia Minor, but was killed by his own soldiers after an indecisive campaign against Probus in the mountains of Cilicia. In contrast to Florian, who ignored the wishes of the Senate, Probus referred his claim to Rome in a respectful dispatch. The Senate enthusiastically ratified his pretensions. Probus next travelled west, defeating the Goths along the lower Danube in 277, and acquiring the title of Gothicus. However, the Goths came to respect his ability and implored a treaty with the empire. In 278, Probus campaigned successfully in Gaul against the Alemanni and Longiones; both tribes had advanced through the Neckar valley and across the Rhine into Roman territory. Meanwhile, his generals defeated the Franks and these operations were directed to clearing Gaul of Germanic invaders (Franks and Burgundians), allowing Probus to adopt the titles of Gothicus Maximus and Germanicus Maximus. Reportedly, 400,000 barbarians were killed during Probus' campaign, and the entire nation of the Lugii were extirpated. After the defeat of the Germanic invaders in Gaul, Probus crossed the Rhine to campaign successfully against the barbarians in their homeland, forcing them to pay homage. In the aftermath of the campaign, Probus repaired the ancient fortifications erected by Hadrian in the vulnerable space between the Rhine and Danube, in the territory of Swabia. More significantly, Probus, by forcing from the vanquished tribes a tribute of manpower, established the precedent of settling barbarians within the empire as auxiliaries on a large scale. The provinces were depopulated by war, disease and the chaotic administration, heavy taxation, and extensive army recruitment, during the Crisis of the Third Century, and the barbarian colonies, at least