<P> Following the death of Jovian, Valentinian I emerged as Emperor in 364 . He immediately divided the Empire once again, giving the eastern half to his brother Valens . Stability was not achieved for long in either half, as the conflicts with outside forces (tribes) intensified . In 376, the Visigoths, fleeing before the Ostrogoths, who in turn were fleeing before the Huns, were allowed to cross the river Danube and settle into the Balkans by the Eastern government . Mistreatment caused a full - scale rebellion, and in 378 they inflicted a crippling defeat on the Eastern Roman field army in the Battle of Adrianople, in which Valens also died . The campaigns to subdue them were only partly successful, and they officially became semi-independent foederati under their own leaders . </P> <P> More than in the East, there was also opposition to the Christianizing policy of the Emperors in the western half of the Empire . In 379, Valentinian I's son and successor Gratian declined to wear the mantle of Pontifex Maximus, and in 382 he rescinded the rights of pagan priests and removed the Altar of Victory from the Roman Curia, a decision which caused dissatisfaction among the traditionally pagan aristocracy of Rome . Theodosius I later decreed a ban on all religions except orthodox Christianity . </P> <P> The political situation was unstable . In 383, a powerful and popular general named Magnus Maximus seized power in the West and forced Gratian's half - brother Valentinian II to flee to the East for aid; in a destructive civil war, the Eastern Emperor Theodosius I restored him to power . In 392, the Frankish and pagan magister militum Arbogast assassinated Valentinian II and proclaimed an obscure senator named Eugenius as Emperor . In 394 the forces of the two halves of the Empire again clashed with great loss of life . Again Theodosius I won, and he briefly ruled a united Empire until his death in 395 . He was the last Emperor to rule both parts of the Roman Empire; his older son Arcadius inherited the eastern half while the younger Honorius got the western half . Both were still minors and neither was capable of ruling effectively . Honorius was placed under the tutelage of the half - Roman / half - barbarian magister militum Flavius Stilicho while Rufinus became the power behind the throne in the east . Rufinus and Stilicho were rivals, and their disagreements were exploited by the Gothic leader Alaric I who again rebelled following the death of Theodosius I. Neither half of the Empire could raise forces sufficient even to subdue Alaric's men, and both tried to use Alaric against the other half . Alaric himself tried to establish a long - term territorial and official base, but was never able to do so . </P> <P> Stilicho tried to defend Italy and bring the invading Goths under control, but to do so he stripped the Rhine frontier of troops and the Vandals, Alans, and Suevi invaded Gaul in large numbers . Stilicho became a victim of court intrigues and was killed in 408 . While the East began a slow recovery and consolidation, the West began to collapse entirely . Alaric's men sacked Rome in 410 . </P>

Who was the first ruler of the western roman empire