Valentinian I (; ; 32117 November 375), sometimes called Valentinian the Great, was Roman emperor from 364 to 375. After ruling the entire empire alone for a month, he made his brother Valens his co-emperor, giving him rule of the eastern provinces. Valentinian retained the west. During his reign, Valentinian fought successfully against the Alamanni, Quadi, and Sarmatians. Most notable was his victory over the Alamanni in 367 at the Battle of Solicinium. His general Count Theodosius defeated a revolt in Africa and the Great Conspiracy, a coordinated assault on Roman Britain by Picts, Scots, and Saxons. Valentinian was also the last emperor to conduct campaigns across both the Rhine and Danube rivers. Valentinian rebuilt and improved the fortifications along the frontiers, even building fortresses in enemy territory. He founded the Valentinianic dynasty, with his sons Gratian and Valentinian II succeeding him in the western half of the empire. Early life Valentinian was born in 321 at Cibalae in southern Pannonia (now Vinkovci in Croatia) into an Illyro-Roman family. Valentinian and his younger brother Valens were the sons of Gratianus Funarius, a prominent commander during the reigns of emperors Constantine I and Constans I. He and his brother grew up on the family estate where they were educated in a variety of subjects, including painting and sculpting. Gratianus was promoted to comes Africae in the late 320s or early 330s, and the young Valentinian accompanied his father to Africa. However, Gratian was soon accused of embezzlement and was forced to retire. Valentinian joined the army in the late 330s and later probably acquired the position of protector domesticus. Gratian was later recalled during the early 340s and was made comes of Britannia. After holding this post, Gratianus retired to the family estate in Cibalae. In 350, Constans I was assassinated by agents of the usurper Magnentius, a commander who proclaimed himself emperor in Gaul. Constantius II, older brother of Constans and emperor in the East, promptly set forth towards Magnentius with a large army. The following year the two emperors met in Pannonia. The ensuing Battle of Mursa Major resulted in a costly victory for Constantius. Two years later he defeated Magnentius again in southern Gaul at the Battle of Mons Seleucus. Magnentius, now realizing the futility of continuing his revolt, committed suicide in August that year; making Constantius sole ruler of the empire. It was around this time that