He acquired Provence by marriage in 1246. Pope Urban IV was under severe threat from the Hohenstaufens and gave him the kingdom of Sicily in order to curtail their power. He defeated and killed Manfred at Benevento, effectively ending Hohenstaufen influence, but then went on to take Naples as well as most of northern Italy, himself becoming a real threat to papal interests. His ambitions were ended by the uprising known as the Sicilian Vespers in which he was assassinated and the French expelled.