Valens has finally assembled enough troops to deal effectively with the usurper Procopius in the spring of 366.

Marching out from Ancyra through Pessinus, Valens proceeds into Phrygia, where he defeats Procopius's general Gomoarius at the Battle of Thyatira.

The defeat of Gomoarius decreases the hopes of Procopius, so that, when Valens reaches Procopius and his troops at Nacoleia, the troops of the usurper desert their commander, and Procopius is on May 27 executed by the army, most of which have remained faithful to Valens, and his head sent to Valentinian in Trier for inspection.