Valentinian I, 321-75, Roman emperor of the West (364-75). He held high military rank under Julian and Jovian. After the death of Jovian, Valentinian was proclaimed emperor; he appointed his brother Valens coregent in the East. Valentinian defeated the Alemanni several times, and his general Theodosius successfully defended the empire in Britain and in Africa. To protect the frontiers of his empire, Valentinian ordered the construction of fortresses on the Rhine and the Danube rivers. He reduced taxation and promoted education. Although he was an orthodox Christian, he allowed religious freedom to Arians and to pagans. He was succeeded by his sons Valentinian II and Gratian.

in full Flavius Valentinianus

(born AD 321, Cibalae, Pannonia—died Nov. 17, 375, Brigetio, Pannonia Inferior) Roman emperor (364–375). He served in the military in Africa under his father. Proclaimed emperor by the army, he made his brother Valens ruler in the East while he ruled the West. Both agreed to allow religious toleration, which Valentinian, unlike Valens, maintained throughout his reign. He defeated the Alemanni in Gaul in 365, then moved to support the defense of Britain. He named his nine-year-old son Gratian coemperor (367) to ensure succession. In Germany he fortified the Rhine; he went on to fight the Quadi in Pannonia, where he fell sick and died. Despite his achievements, he was known for his cruelty and poor choice of ministers.

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