Valentinian I (321-375), also known as Valentinian the Great, was the son of Gratianus Major, a commander under emperors Constantine I and Constans I. Valentinian joined the army in the late 330s, but he was humiliated and his career ruined during a debacle against Alamanni raiders caused by the incompetency of others. His fortunes would swiftly change when he was promoted to tribune by Emperor Jovian, whose later death led to Valentinian's ascension to emperor by civil and military assembly in 364. He selected his brother Valens as co-emperor of the east, while Valentinian managed the west. He successfully fought off various Germanic and barbarian invasions, as well as dealing with revolts in Africa and the Great Conspiracy, a massive attack on Britain by Picts, Saxons and Scots. Valentinian became the last emperor to conduct campaigns across the Danube and Rhine rivers, building and improving fortresses and fortifications along the frontiers and even in enemy territory. His successes and the rapid decline that occurred after his death led many to consider Valentinian the 'last great western emperor', and he died in 375 from a burst blood vessel while angrily yelling at Quadi envoys. His sons would succeed him, making him the founder of the Valentinian Dynasty.