Like his father, he began his military conquests in the Abruzzi, encroaching on lands held by the Roman pontiff.
In return for his uncle's help, he sent a contingent of his own men to assist in the defeat of his cousin Abelard in Sant'Agata di Puglia.
In June 1080, Gregory VII recognised the Norman conquests of Robert and Jordan up to Fermo.
In June 1083, besieged in the Castel Sant'Angelo by the Emperor Henry IV, the pope begged the assistance of the duke.
He was at the Guiscard's deathbed and remained loyal to his uncle's chosen heir, Roger Borsa, whose guardian he had been.