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Charles of Anjou had been King of Sicily for about 2 years when he defeated an invasion by the legitimate King of Sicily, Conrad II (aka Conradin), who was also Duke of Swabia and King of Jerusalem through his grandmother. IOTL Conradin was defeated, captured and executed.

What if Charles had lost and Conrad had won? Calabria, Apulia and most of Sicily has risen up in support of him.
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