several months in Cyprus they invaded Egypt on 5June 1249. They captured Damietta and decided to attack Cairo in November. During their advance Louis's biographer Jean de Joinville noted Charles's personal courage which saved dozens of crusaders' lives. Robert of Artois died fighting against the Egyptians at Al Mansurah. His three brothers survived, but they had to abandon the campaign. While withdrawing from Egypt, they fell into captivity on 6April 1250. The Egyptians released Louis, Charles and Alphonse in exchange of 800,000 bezants and the surrender of Damietta on 6May. During their voyage to Acre, Charles outraged Louis by gambling while the king was mourning Robert's death. Louis remained in the Holy Land, but Charles returned to France in October 1250. Wider ambitions Conflicts and consolidation Charles's officers continued the survey of the counts' rights and revenues in Provence, provoking a new rebellion during his absence. On his return he applied both diplomacy and military force to deal with them. The Archbishop of Arles and the Bishop of Digne ceded their secular rights in the two towns to Charles in 1250. He received military assistance from his brother, Alphonse. Arles was the first town to surrender to them in April 1251. In May they forced Avignon to acknowledge their joint rule. A month later Barral of Baux also capitulated. Marseilles was the only town to resist for several months, but it also sought peace in July 1252. Its burghers acknowledged Charles as their lord, but retained their self-governing bodies. Charles's officials continued to ascertain his rights, visiting each town and holding public enquiries to obtain information about all claims. The count's salt monopoly (or ) was introduced in the whole county. Income from the salt trade made up about 50% of state revenues by the late 1250s. Charles abolished local tolls and promoted shipbuilding and grain trade. He ordered the issue of new coins, called , to enable the use of the local currency in smaller transactions. Emperor Frederick II, who was also the ruler of Sicily, died in 1250. The Kingdom of Sicily, also known as the Regno, included the island of Sicily and southern Italy nearly as far as Rome. Pope Innocent IV claimed that the Regno had reverted to the Holy See. The Pope first offered it to Richard of Cornwall, but Richard did not want to fight against Frederick's son, Conrad IV of Germany. Then the