When the Norman noble, Osmond Drengot, was exiled by Duke Richard II of Normandy for the murder of one of his relatives, Osmond, and his 4 brothers (including Gilbert Buatère and Rainulf Drengot) went on a pilgrimage to the shrine of Saint Michael, at Monte Sant-Angelo sul Gargano in the Byzantine Catepanate of Italy.

In 1016, this Norman band was recruited by the Lombard noble Melus (or Melo) of Bari, who had rebelled against his Byzantine overlords but who was currently on the run. Melus assured the Norman adventurers of the ease of victory and the abundance of spoils.

In1017, the Normans were heading south. They joined with the Lombard forces under Melus at Capua and marched into Apulia, trying to catch the Byzantines off-guard. Successful in 5 successive encounters against forces sent by the catapan Kontoleon Tornikios, they had seized all the territory between the Fortore and Trani by September and were ravaging Apulia. The Norman leader in this phase was Gilbert Buatère.