in Pannonia (351 A. D.), where the
victory was won by the mailed horsemen of Constantius, who from this time
onwards formed the most effective arm in the Roman service. In the next
year Constantius recovered Italy, and in 353 invaded Gaul, whereupon
Magnentius took his own life.

*Gallus, Caesar, 351-4 A. D.* Constantius had no son, and so to strengthen
his position, he made his cousin, Gallus, Caesar and placed him in charge
of the Orient when he set out to meet Magnentius in 351 A. D. But Gallus
soon showed himself unworthy of his office. His mistreatment of the
representatives of the emperor sent to investigate his conduct caused him
to be suspected of treasonable ambitions, and he was recalled and put to
death in 354 A. D.

*Julian, Caesar, 335 A. D.* However, Constantius still found himself in
need of an associate in the _imperium_. In addition to the danger of
invasion on both northern and eastern frontiers, came the revolt of
Silvanus at Cologne in 355, which, although quickly suppressed, was a
reminder that every successful general was potentially a candidate for the
throne. Accordingly, at the advice of the empress Eudoxia, he called from
the enforced seclusion of a scholar's life Julian, the younger brother of
Gallus, whom he made Caesar and dispatched to Gaul (355 A. D.). Since the
fall of Magnentius the Gallic provinces had been exposed to the
devastating incursions of Franks and Alemanni, and the first task of the
young Caesar was to deal with these barbarians. In a battle near
Strassburg in 357 he broke the power of the Alemanni, and drove them over
the Rhine. The Franks were forced to acknowledge Roman overlordship, but
the Salian branch of that people were allowed to settle to the south of
the Rhine (358 A. D.). In addition to displaying unexpected capacities as
a general, Julian showed himself a forceful and upright administrator,
whose chief aim was to revive the prosperity of his sorely-tried
provincials.

*Julian, Augustus, 360 A. D.* In 359 A. D. a fresh invasion of Mesopotamia
by Sapor II called Constantius to the East. The seriousness of the
situation there caused him to demand considerable reinforcements from the
army in Gaul. This was resented both by the soldiers themselves and by
Julian, who saw in the order a prelude to his own undoing, for he knew the
suspicious nature of his cousin, and was aware that his own successes and
the restraint he imposed upon the rapacity of his officials had ar