In summer 546, Justinian chose John Troglita to assume overall command of Byzantine forces in Africa, where a succession of revolts by the indigenous Moorish tribes and within the imperial army itself had seriously reduced the Byzantine position. Troglita quickly secured an initial victory in the winter of 546/547 against the Moors of Byzacena, but was defeated in summer 547 by the tribes of Tripolitania, and Africa was once again laid open to destructive raids. Troglita reorganized his army and secured the assistance of some tribal leaders, and confronted and decisively defeated the tribal coalition at the Fields of Cato in summer 548.