In summer 599, the East Roman Emperor Maurice sent his generals Priscus and Comentiolus to the Danube front against the Avars. The generals joined their forces at Singidunum and advanced together down the river to Viminacium. The Avar khagan Bayan I meanwhile, learning that the Romans had determined to violate the peace, crossed the Danube at Viminacium and invaded Upper Moesia, while he entrusted a large force to four of his sons, who were directed to guard the river and prevent the Romans from crossing over to the left bank. In spite of the presence of the Avar army, however, the East Roman army crossed on rafts and pitched a camp on the left side, while the two commanders sojourned in the town of Viminacium, which stood on an island in the river. Here Comentiolus is said to have fallen