Answer
The Sicilian Vespers was a popular uprising in 1282 against the French Angevin rulers of Sicily. It was caused by the French massacre of the Sicilians at Easter Mass, and it resulted in the expulsion of the French from the island. The Sicilian Vespers also caused the return of the County of Alençon to the crown lands, as the count of Alençon was one of the leaders of the uprising.