Frederick was an effective ruler for the first decade and Sicily was more prosperous than it had been in decades. Still, Robert of Naples was bitter that the Angevins had lost Sicily from his kingdom. The Roman Curia had refused Robert's request in 1302 for a crusade against Sicily. Southern Italy and Sicily were considered by the Pope to be part of the Church's patrimony, second only to the Papal State. This alliance between the papacy and Robert of Naples was strong because of this. It was further strengthened in 1308 when Pope Clement V moved the papacy to Avignon. Robert had strong connections with powerful people in France, so moving the papacy to Avignon only strengthened relations. With the constant threat from Naples, Frederick allied Sicily with the Ghibelline league in 1310. He saw this as an opportunity to protect Sicily from the Angevins, as the Italian expedition by Emperor Henry VII in 1310-1313 helped to increase Ghibelline power in northern and central Italy. Robert of Naples was becoming frustrated with the Sicilian situation and renewed war in 1313. Henry's unexpected death in 1313 increased Robert's resolve. In 1315, Frederick of Austria hoped to marry his sister Catherine to Frederick's son Peter. Instead, Robert, hoping to interrupt an Imperial-Sicilian alliance, married Catherine to his son Charles. During this time, the Angevins and Frederick's brother James of Aragon tried to convince the King of Sicily to trade his kingdom in exchange for Achaea and Albania. Frederick declined this request, but Robert of Naples continued this dialogue in 1316-1317, even offering the western half of Sicily along with the lands previously offered. Frederick wanted no part of these other lands and Pope John XXII established a truce between these feuding kingdoms in 1317. However, Robert remained bitter, and in 1320 war broke out between the Angevins and the Sicilians.