The battle had its origin in the decision of Arduin the Lombard, a Greek-speaking Lombard who had fought for the Byzantines, to change sides and form a coalition with the Normans Rainulf Drengot and the Hauteville brothers (William Iron Arm, Drogo, Humphrey), and the Lombards Atenulf of Benevento and Argyrus of Bari. Once having defeated the imperial armies, they would take for themselves the conquered lands.