As emperor Valens continually faced threats both internal and external. He defeated, after some dithering, the usurper Procopius in 366, and campaigned against the Goths across the Danube in 367 and 369. In the following years, Valens focused on the eastern frontier, where he faced the perennial threat of Persia, particularly in Armenia, as well as additional conflicts with the Saracens and Isaurians. Domestically, he inaugurated the Aqueduct of Valens in Constantinople, which was longer than all the aqueducts of Rome. In 376–77, the Gothic War broke out, following a mismanaged attempt to settle the Goths in the Balkans. Valens returned from the east to fight the Goths in person, but lack of coordination with his nephew, the western emperor Gratian (Valentinian I's son), as well as poor battle tactics, led to Valens and much of the eastern Roman army dying at a battle near Adrianople in 378.