Reign
Frederick reformed the administration and extended the powers of the Sicilian parliament, which was composed of the barons, the prelates, and the representatives of the towns.
His refusal to comply with the pope's injunctions led to a renewal of the war. Frederick landed in Calabria, where he seized several towns, encouraged revolt in Naples, negotiated with the Ghibellines of Tuscany and Lombardy, and assisted the house of Colonna against Pope Boniface. In the meantime, James, who received many favours from the Church, married his sister Yolanda to Robert, the third son of Charles II. Unfortunately for Frederick, a part of the Catalan-Aragonese nobles of Sicily favoured King James, and both John of Procida and Roger of Lauria, the heroes of the war of the Vespers, went over to the Angevins, and the latter completely defeated the Sicilian fleet off Capo d'Orlando. Charles's sons Robert and Philip landed in Sicily, but after capturing Catania were defeated by Frederick, Philip being taken prisoner (1299), while several Calabrian towns were captured by the Sicilians.
For two years more the fighting continued with varying success, until Charles of Valois, who had been sent by Boniface to invade Sicily, was forced to sue for peace, his army being decimated by disease. In August 1302 the Treaty of Caltabellotta was signed, by which Frederick was recognised king of Trinacria (the name Sicily was not to be used) for his lifetime, and was to marry Eleanor of Anjou, daughter of Charles II of Naples and Maria Arpad of Hungary. At Frederick's death, the kingdom was to revert to the Angevins (this clause was inserted chiefly to allow Charles to save face) and Frederick's children would receive compensation elsewhere. Boniface tried to induce King Charles to break the treaty, but the latter was only too anxious for peace. Finally, in May 1303, the pope ratified the treaty, albeit with changes and additions, which included Frederick agreeing to pay him a tribute.
For a few years Sicily enjoyed peace, and the kingdom was reorganised. However, on the descent of the emperor Henry VII, Holy Roman Emperor into Italy, Frederick entered into an alliance with him, and in violation of the pact of Caltabellotta made war on the Angevins again (1313) and captured Reggio. He set sail for Tuscany to cooperate with the emperor, but on the latter's death he returned to Sicily. Robert, who had succeeded Charles II in 1309, made several raids into the island, which suffered much material injury. A truce was concluded in 1317, but as the Sicilians had helped the Lombard Ghibellines in the attack on Genoa, and Frederick had seized some Church revenues for military purposes, Pope John XXII excommunicated him and placed the island under an interdict (1321) which lasted until 1335. An Angevin fleet and army, under Robert's son Charles, was defeated at Palermo by Giovanni da Chiaramonte in 1325, and in 1326 and 1327 there were further Angevin raids on the island, until the descent into Italy of the next Holy Roman Emperor Louis the Bavarian distracted their attention. The election of Pope Benedict XII (1334), who was friendly to Frederick, promised a respite; but after fruitless negotiations the war broke out once more, and Chiaramonte went over to Robert, owing to a private feud.
In 1337 Frederick died at Paternò, and in spite of the Peace of Caltabellotta his son Peter II of Sicily succeeded him.
