In 400, Gainas, rebellious former Roman "magister militum" fled into Uldin's territory with an army of Goths, and Uldin defeated and killed him, likely near Novae: he sent Gainas's head to Constantinople. Kim suggests that Uldin was interested in cooperating with the Romans while he expanded his control over Germanic tribes in the West. In 406, Hunnic pressure seems to have caused groups of Vandals, Suebi, and Alans to cross the Rhine into Gaul. Uldin's Huns raided Thrace in 404–405, likely in winter.