The War of the Sicilian Vespers, also shortened to the War of the Vespers, was a conflict waged by several medieval European kingdoms over control of Sicily from 1282 to 1302. The war, which started with the revolt of the Sicilian Vespers, was fought over competing dynastic claims to the throne of Sicily and grew to involve the Kingdom of Aragon, Angevin Kingdom of Naples, Kingdom of France, and the papacy.
Initially fought between Sicilian rebels and Charles of Anjou in Sicily and Southern Italy, the war expanded when Aragon invaded Sicily to support the rebels and claim the throne. After Aragonese successes, the war grew into the concurrent Aragonese Crusade as the Kingdom of France intervened against Aragon in Iberia. The crusade ended in defeat, but efforts to end the war failed despite several peace treaties. Aragon gave up the crown of Sicily in exchange for papal concessions in 1297, entering into an alliance with Angevin Naples and the papacy against Sicily, but the new alliance's campaign to invade Sicily saw no success. The war ended in 1302 in the Peace of Caltabellotta, by which Sicily became an independent kingdom ruled by the House of Barcelona.
The war resulted in the division of the old Kingdom of Sicily; the island of Sicily came to be ruled as the Kingdom of Sicily, while the mainland territories of the old kingdom became the Kingdom of Naples. The war led to an era of Aragonese expansion in the Western Mediterranean, as the kingdom gained suzerainty over the Kingdom of Majorca and Sardinia. Outlasting four kings and four popes, the twenty-year war showcased the decline of papal power in southern Europe and the rise of increasingly powerful kings in the late 13th century.
Background
Papal concerns & competing claims over Sicily
The island of Sicily had ruled as a medieval kingdom since the early 12th century, when Roger II of Sicily conquered the island and established the Kingdom of Sicily. Strategically located in the Mediterranean, the kingdom grew to include much of southern Italy, and was considered one of the wealthiest kingdoms in Europe. Grain produced in the kingdom's lands in Sicily and southern Italy contributed to feeding the northern Italian city states and the Holy Land, while the island of Sicily itself served as a staging ground for various crusades. Sicily was key to the defense of Rome and the papal states, and as such the papacy considered it vital that a friendly king occupied the throne of Sicily. Diplomatic relations between the papacy and Sicily were heavily intertwined; the pope had funded the Norman invasion of Sicily and sanctioned the establishment of the kingdom, and the king of Sicily officially held the throne as a vassal in the name of the pope.
In the 13th century, Sicily became the heartland of the Hohenstaufen empire of Frederick II of Sicily. Frederick and the pope bitterly disagreed on issues of papal authority, and his rule resulted in a flare-up of the centuries long conflict between the pro-pope Guelphs and pro-imperial Ghibellines. When Frederick died the kingdom of Sicily was claimed by Manfred I of Sicily, his illegitimate son, who quarreled with the pope over his legitimacy as king. Seeing the opportunity created by Manfred's contested claim to the throne of Sicily, in the 1250s the papacy began to look for a potential claimant to overthrow him.
Conquest of Sicily by Charles of Anjou
At papal invitation, in 1265 the kingdom of Sicily was invaded and conquered by Charles I of Anjou, a powerful member of the French royal House of Capet. Manfred of Sicily was drawn into a battle and killed, and Charles' victory allowed him to establish the Angevin Kingdom of Sicily and Naples, giving him control of Sicily and most of southern Italy. Using the ongoing conflict between the Guelphs and Ghibellines as a political wedge, Charles expanded his influence throughout Italy, cobbling together a formidable feudal state and forcing treaties on many Italian cities. With Sicily and Naples under his control, Charles and his brother, King Philip III of France, were able to greatly increase French influence in the western Mediterranean. The papacy heavily benefited from the Angevin conquest, as the usurping of Manfred's throne by Charles of Anjou ensured a pro-papacy king ruled over Sicily, and Manfred's death deprived the anti-papacy Ghibellines of one of their greatest supporters in Italy.