The Normans join with the Lombard forces under Melus at Capua and march into Apulia immediately, trying to catch the imperial forces off-guard.

Successful in an encounter in May on the banks of the Fortore against forces sent by the katapano Leo Tornikios Kontoleon, they have seized all the territory between the Fortore and Trani by September and are ravaging Apulia; in October, however, they experience a stunning reverse.

The new katepano, Basil Boiannes, appointed in December 2017, has garnered a massive force of reserves and a contingent of the famed Varangian Guard from Emperor Basil II.

He meets the Norman and Lombard hosts on the Ofanto at the site of the famous defeat dealt the Romans by Hannibal in 216 BCE: Cannae.

This second battle of Cannae is a disaster both for the Normans and for the Lombards.

Of the two hundred and fifty Norman knights under Gilbert's command, Gilbert himself, along with Osmond, die in the battle: only ten knights survive.

The Lombard leaders flee: Melus to the "Samnite lands" (Amatus) of the Papal States and Dattus to Montecassino and the tower again.

Melus will continue wandering through south and central Italy and finally northwards to Germany, ending up at the imperial court of Henry II in Bamberg.

Though greatly honored (he receives the empty title Duke of Apulia from the emperor), he will die a broken man only two years later, just after Pope Benedict arrives in Bamberg at Eastertide to discuss a response by the Western Empire to Constantinople’s victories.

He will be given a lavish funeral and an ornate tomb in the new Bamberg Cathedral by his old ally, the emperor.

His son Argyrus will carry on the struggle for Lombard independence in Apulia after his return from imprisonment in Constantinople.