In 367, the Roman Emperor Valens attacked the Thervingi north of the Danube river in retribution for their having supported the usurper Procopius, who had died in 366. However, he was unable to hit them directly, because apparently the bulk of the Goths retreated to the Montes Serrorum (which is probably the south Carpathians). Ammianus Marcellinus says that Valens could not find anyone to fight with (nullum inveniret quem superare poterat vel terrere) and even implies that all of them fled, horror-struck, to the mountains (omnes formidine perciti... montes petivere Serrorum). In the following year, the flooding of the Danube prevented the Romans from crossing the river.