Valentinian I in Wikipedia

Flavius Valentinianus (321 – 17 November 375), commonly known as Valentinian I or Valentinian the Great[1], was Roman Emperor from 364 to 375. He was the last emperor to have de facto control of the entire empire. Upon becoming emperor he made his brother Valens his co-emperor, giving him rule of the eastern provinces while 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 brilliant general Count Theodosius defeated a revolt in Africa and the Great Conspiracy, a coordinated assault on Britain by Picts, Scots, and Saxons. Valentinian was also the last emperor to conduct campaigns across the Rhine and Danube rivers. He rebuilt and improved the fortifications along the frontiers – even building fortresses in enemy territory. Due to the successful nature of his reign and almost immediate decline of the empire after his death, he is often considered the "last great western emperor". He founded the Valentinian Dynasty, with his sons Gratian and Valentinian II succeeding him in the western half of the empire...