Frederick and the papacy bitterly disagreed on issues of papal authority, and his rule resulted in a violent flare-up of the centuries long conflict between the pro-pope Guelphs and pro-imperial Ghibellines.

[8][6] Using the conflict between the Guelphs and Ghibellines as a political wedge, the victorious Charles expanded his influence throughout Italy, cobbling together a formidable feudal state and forcing treaties on many Italian cities.

From 1272 to 1276, the Angevin kingdom fought against the Republic of Genoa after Charles detained Genoese merchants in his territory,[12] while also sending troops to drive Ghibellines supporters out of Siena, Pisa, and Tuscany.

[12] Charles had a longstanding ambition to act on the 1267 Treaty of Viterbo, which nominally gave him and his heirs the right to conquer large parts of the Byzantine Empire, and in 1271 he seized control of Corfu and costal Albania.

Charles was also elected Senator of Rome and imperial vicar of Tuscany, and appointed officials to govern parts of the former city in his name, thus securing a solid base of political power for the Angevin kingdom.

Muslim victories against Christian fiefdoms in the Levant were destabilizing the Holy Land, and it became widely speculated that Charles and the Angevins would soon sail to invade Byzantium; both of these occurrences sparked fears of a renewed campaign of forced conscription and taxation in Sicily.

[12][16] These fears were seemingly confirmed when in December 1281, Charles ordered a 50 percent increase in the traditional subventio generalis tax for the coming year, which mandated the populace pay or enter military service.

Hoping to bolster the city's defenses, in April Herbert sent Angevin troops to reinforce the mountain forts that circled Messina, but this action backfired and emboldened the increasingly pro-rebel populace.

Captain of the People Alaimo da Lentini [it] took command of the city on behalf of the rebellion and rioters burned the Angevin crusader fleet stationed in the harbor, greatly hampering Charles' ambitions in the Mediterranean.

Peter accepted the offer of the Sicilian throne, while informing the papal envoys that he was still planning on crusading in North Africa—a cover story he continued to use as his fleet sailed towards Sicily.

Aragonese troops led by prince James of Aragon landed on the Italian mainland, marching toward Reggio without resistance, but no large uprising against Charles took place in wider Calabria.

Having seen his fleet fail to prevent the Aragonese conquests of Sicily and Malta, he replaced his admirals and captains with new men, who he hoped would be more capable, and hired mercenary ships from Genoa and Pisa to supplement his forces.

[24][25] The huge costs incurred by the naval buildup and aborted land campaign depleted the Angevin treasury—crippling debt, and the unexpected series of Aragonese victories, forced Charles to halt his counterattack until 1285.

[24] Though it maintained control over Naples and much of Southern Italy, the Angevin Kingdom lacked the funds to continue the counter offensive against Aragon, and with his son's capture, Charles had lost his heir.

Local nobles conducted a scorched earth campaign against the French, prompting Philip to order his army to isolate any Aragonese garrison they encountered and continue south quickly, fearful of running out of supplies.

[3][26] Philip made slow but consistent progress southward, and by late June 1284 the French army had reached Girona, laying siege to the city in the heat of the Catalan summer.

With France's military strength sapped by the losses incurred during the crusade, the newly crowned Philip IV chose to not pursue further conflict with Aragon in Iberia.

The regent of Naples, Robert II of Artois, proved to be a capable administrator and used Aragon's war with France in Iberia as an opportunity to rebuild the Angevins' battered armies and fleets.

Moving north into the Aegean, Lauria's force mounted a large raid on the Genoese-held island of Chios, plundering a fortune in Mastic gum, before turning south to attack the Angevin-ruled Principality of Achaea.

The fleet returned to Sicily in late summer, stopping to raid Corfu a second time and possibly making an aborted attack on Brindisi, before docking in Messina on 21 September 1292.

[32] In October a small Sicilian squadron intercepted and routed an Angevin fleet trying to raid Ischia, enraging Charles II and causing him and Boniface to redouble their efforts to have James and Aragon re-enter the war on their side.

[32] In Rome, James negotiated a new treaty in which he agreed to make war on his brother and Sicily in exchange for further compensation, namely money and a papal sanction to annex Sardinia and Corsica.

Frederick's new position in the central Sicilian highlands moved him away from the larger costal cities, but also strengthened his internal lines of communication, as from Enna's commanding plateau he was able to send out forces to counter the Angevins wherever they chose to attack.

[35] Having captured Catania and isolated Messina and Syracuse in the east, the Angevins now prepared an invasion of western Sicily, hoping to catch Frederick's remaining forces in a pincer.

Faced with a choice of waiting in heavily-fortified Enna to be trapped between the eastern and western Angevin armies or going on the offensive, Frederick consolidated his forces and marched to attack Philip in the west.

Seeing that Messina could not be starved into submission and facing a blistering series of small Sicilian attacks, Roger and Robert agreed to withdraw all Angevin soldiers on the island to Catania.

[36] Faced with Charles of Valois' large and professional French army, Frederick chose to fortify coastal towns and scour the countryside of food, planning to wear down the invaders in a war of attrition.

Marriage was arranged between Frederick and Charles' daughter Eleanor to tie the Sicilian House of Barcelona to Angevin Naples, and the papacy agreed to cede its claim to hold Sicily as a vassal kingdom.

[40] The war contributed to the decisive defeat of the Crusader States at the Siege of Acre, as the Vesperan conflict left the major Christian powers of Europe unwilling to commit troops to the Holy Land.

[13] Italian historian and political activist Michele Amari wrote a popular history of the conflict (La guerra del vespro siciliano, published 1842), which became widely circulated among independence agitators on the island.