Attacks and blockades became common in the 1320s. The Sicilians were able to hold out against the Angevins, but the people of Sicily saw their living standards deteriorate. The people still remained loyal to Frederick as they disliked the Angevins more. In 1322, the Sicilians swore fealty to Frederick's son Peter, thus officially breaking the terms set up at Caltabellotta. Crusades against the Ghibellines, who were important trading partners with Sicily, began in 1320 and lasted until 1334. Though not directly attacked, this was another hardship that Frederick and his kingdom had to deal with. Frederick was given hope by the fact that Emperor Louis IV intervened in northern Italy in 1323, protecting Milan from an invasion by Naples. This drew Pope John's attention to the north. In 1325, the Angevins and Charles of Calabria requested a crusade against Sicily. However, Pope John rejected this request, stating that it would hurt papal authority and that Frederick had not reached a level where this last resort was necessary. This refusal may have saved Sicily from being conquered. Papal policy was less aggressive towards Sicily under John XXII and Benedict the XII. In 1328, Emperor Louis invaded Italy, taking Rome. From the Sicilian perspective, an invasion of Naples seemed to be the next step. However, Frederick and Louis made mistakes in coordinating their forces and sending Sicilian food supplies to the Emperor's army. This resulted in Louis fleeing Rome. Things only got worse for the Sicilians as the Ghibelline coalition disintegrated and Louis left Italy in 1330, never to return. Sicily was left in a very vulnerable position. Angevin campaigns continued with separate attacks occurring in 1325-26, 1327, 1333, and 1335. The Sicilians were able to prevail, but by this point they had exhausted all of their resources.