On Easter Monday, 1282, a French soldier made a fatal mistake outside a church in Palermo. Within hours, thousands of his countrymen were dead across the island of Sicily, and the most powerful monarch in the Mediterranean world ? Charles I of Anjou, who had been assembling a fleet to conquer Constantinople ? found himself facing the destruction of everything he had built. The bells that rang that night changed the map of the world.

Carlos O'Boyle's The Bell That Changed the World reconstructs the War of the Sicilian Vespers in full narrative sweep ? twenty years of conflict that pitted the might of France, the papacy, and the Angevin dynasty against a single island population that refused to be governed by people it had not chosen. This is the story of Roger of Lauria, the greatest admiral of the medieval Mediterranean, whose fleet decided the war in the waters around Sicily; of Peter III of Aragon, whose audacity converted a popular uprising into a dynastic empire; of Frederick III, the island's own king, who held his throne against every treaty and every army Europe could assemble; and of the unnamed Sicilian farmers, mothers, and craftspeople who paid the war's real cost in silence.

Gripping, rigorously researched, and written with the urgency of the finest narrative history, this is the story of how a crowd, a church, and a bell cracked the medieval world open.