William's poem "Gesta Roberti Wiscardi" was probably composed sometime between 1097 and 1099, as he notes the fighting of the crusaders in Anatolia during 1097, but not the fall of Jerusalem in 1099. The poem was dedicated to Duke Roger Borsa son of duke Robert Guiscard, implying that he was a member of the former's court. More than the works of his two fellow chroniclers of the Normans, Amatus of Montecassino and Geoffrey Malaterra, William's work is a tribute to Robert Guiscard, which may indicate that Roger commissioned it to strengthen his claim to his father's titles.