Balkans operations

By the mid-550s, Justinian had won victories in most theatres of operation, with the notable exception of the Balkans, which were subjected to repeated incursions from the Slavs and the Gepids. Tribes of Serbs and Croats were later resettled in the northwestern Balkans, during the reign of Heraclius. Justinian called Belisarius out of retirement and defeated the new Hunnish threat. The strengthening of the Danube fleet caused the Kutrigur Huns to withdraw and they agreed to a treaty that allowed safe passage back across the Danube.