Valens was the Eastern Roman Emperor from 364 to 378. He was given the eastern half of the empire by his brother Valentinian I after the latter's accession to the throne. Valens, sometimes known as the Last True Roman, was defeated and killed in the Battle of Adrianople, which marked the beginning of the collapse of the decaying Western Roman Empire.
Valens and his brother Valentinian were both born in Cibalae (in present-day Croatia) into an Illyrian family in 328 and 321 respectively. They had grown up on estates purchased by their father Gratian the Elder in Africa and Britain. While Valentinian had enjoyed a successful military career prior to his appointment as emperor, Valens apparently had not. He had spent much of his youth on the family's estate and only joined the army in the 360s, participating with his brother in the Persian campaign of Emperor Julian.
In February 364, reigning Emperor Jovian, while hastening to Constantinople to secure his claim to the throne, was asphyxiated during a stop at Dadastana, 100 miles east of Ankara. Among Jovian's agents was Valentinian, a tribunus scutariorum. He was proclaimed Augustus on 26 February, 364. Valentinian felt that he needed help to govern the large and troublesome empire, and, on 28 March of the same year, appointed his brother Valens as co-emperor in the palace of Hebdomon. The two Augusti travelled together through Adrianople and Naissus to Sirmium, where they divided their personnel, and Valentinian went on to the West.
Valens obtained the eastern half of the Empire Greece, Egypt, Syria and Anatolia as far east as Persia. Valens was back in his capital of Constantinople by December 364.