The decline of the Roman Empire saw the classical cities fall into ruin, a process hastened by the Vandals' destructive sweep through North Africa in the 5th century. When the Empire returned (now as East Romans) as part of Justinian's reconquests of the 6th century, efforts were made to strengthen the old cities, but it was only a last gasp before they collapsed into disuse. Cyrenaica, which had remained an outpost of the Byzantine Empire during the Vandal period, also took on the characteristics of an armed camp. Unpopular Byzantine governors imposed burdensome taxation to meet military costs, while the towns and public services—including the water system—were left to decay. By the beginning of the 7th century, Byzantine control over the region was weak, Berber rebellions were becoming more frequent, and there was little to oppose Muslim invasion.