Upon the death of Peter III of Aragon in 1285, his realm in Spain and Sicily passed first to his short-lived older son Alphonso III and then in 1291 to Alphonso's devious and craven brother James II. James appointed his younger brother Frederick as his regent for Sicily, retaining the crown for himself.

The conflict between Aragon and Anjou arising over control of Sicily continued abated. In 1295, shaken by some military reverses, James entered a treaty that--through Pope Boniface VIII as intermediary--purported to surrender the island of Sicily to the Anjou French. The capitulation was particularly shameful in view of the fact that the Anjou French's earlier period of control over the island had begun with murder of Alphonso's own grandfather Manfred after the Battle of Benevento in 1266, and had ended in 1282 with revolt by the long-suffering Sicilian people because of the cruel treatment they suffered at the hands of the Anjou French.

Rule by the Anjou French was as unacceptable to the Sicilians in 1295 as it had been in 1282. This time they found their ally in their regent Frederick, who joined the Sicilians in rejecting a return to Anjou French rule. Frederick was crowned king of the island of Sicily in 1296, and he defended his crown through six years of warfare with forces of both the Pope and the Anjou French. Finally, in 1302 Frederick's forces prevailed and his reign was accepted by the Pope and Anjou French. As a face-saving device for his opponents, Frederick agreed to marry the daughter of Charles II of Anjou and allow the island to pass to the Anjou French upon his death. In fact, no such transfer was actually intended or, indeed, expected.

Until his death in 1337 Frederick's reign was punctuated by periodic warfare with the Pope, whom Frederick periodically enraged by siding with the Holy Roman Empire and its Ghibelline allies of northern Italy in their conflicts with the Pope. Frederick's reign was important in forging a common national spirit among the people of his island kingdom.