Charles was crowned king in Rome on 5 January 1266. He annihilated Manfred's army and occupied the Regno almost without resistance. His victory over Manfred's young nephew, Conradin, at the Battle of Tagliacozzo in 1268 strengthened his rule. In 1270 he took part in the Eighth Crusade organized by Louis IX, and forced the Hafsid Caliph of Tunis to pay a yearly tribute to him. Charles' victories secured his undisputed leadership among the Papacy's Italian partisans (known as Guelphs), but his influence on papal elections and his strong military presence in Italy disturbed the popes. They tried to channel his ambitions towards other territories and assisted him in acquiring claims to Achaea, Jerusalem and Arles through treaties. In 1281 Pope Martin IV authorised Charles to launch a crusade against the Byzantine Empire. Charles' ships were gathering at Messina, ready to begin the campaign when a riotknown as the Sicilian Vespersbroke out on 30March 1282 which put an end to Charles' rule on the island of Sicily. He was able to defend the mainland territories (or the Kingdom of Naples) with the support of France and the Holy See. Charles died while making preparations for an invasion of Sicily.