Norman adventurers had begun a prolonged and haphazard migration to Sicily and southern Italy early in the eleventh century, serving the local nobility as mercenaries fighting the Arabs.

In 999, according to Amatus of Montecassino, pilgrims returning from Jerusalem had called in at the port of Salerno, when a Saracen attack occurred.

The Normans had fought so valiantly that Prince Guaimar III had begged them to stay, but they had refused and instead offered to tell others back home of the prince's request.

The Lombard nobleman Melus and his brother-in-law Dattus had rebelled against Constantinople in 1009 and quickly taken Bari itself, and Ascoli and Troina the following year, but the new catepan, Basil Mesardonites, had gathered a large army.

When Bari fell on June 11, 1011, Melus had fled to the protection of Prince Guaimar III of Salerno and Dattus to the Benedictine abbey of Montecassino, where the anti-Greek monks, at the insistence of Pope Benedict VIII, had given him a fortified tower on the Garigliano.

Melus' family, however, had been captured and carted off to Constantinople.

According to the Norman chronicler William of Apulia, Melus had gone to the shrine of Saint Michael at Monte Gargano in 1016 to intercept some Norman pilgrims.

There he had petitioned Rainulf Drengot and a band of Norman exiles to aid in his rebellion, assuring them of the ease of victory and the abundance of spoils.

By 1017, Norman adventurers are already heading south.

Osmond Buatère, according to some sources, or his brother Gilbert, according to others, had in 1016 killed one William Repostel, a relative of Duke Richard II of Normandy, in revenge for his sleeping with one of Osmond's daughters.

The duke had pardoned his life, but exiled him.

Osmond and his four brothers—Gilbert, Asclettin, Ralph, and Ranulf—travel to the Mediterranean to assist the Lombards in their revolt against imperial pretensions.