Some Norman adventurers, on pilgrimage to Monte Sant'Angelo sul Gargano, lent their swords in 1017 to the Lombard cities of Apulia against the Byzantines. From 1016 to 1030 the Normans were pure mercenaries, serving either Byzantine or Lombard, and then Duke Sergius IV of Naples, by installing their leader Ranulf Drengot in the fortress of Aversa in 1030. This gave the Normans their first foothold in southern Italy from which they began an organized conquest of the land. In 1030, William and Drogo, the two eldest sons of Tancred of Hauteville, a noble of Coutances in Normandy arrived in southern Italy. The two joined in the organized attempt to wrest Apulia from the Byzantines, who had lost most of that province by 1040. Bari was captured by the Normans in April 1071, and Byzantine authority was finally terminated in Italy, five centuries after the conquests of Justinian I. In 1154-1156, through a plan hatched by Emperor Manuel I Komnenos, the Byzantines returned briefly to besiege Bari and were moderately successful in inciting a mass revolt which nearly toppled Norman control (potentially handing much of the former Katepanate back to the Byzantine Empire), but the gains were "reversed by misfortune".