Unfortunately for Michael VIII, the new union was seen as a fake by Clement's successor, Martin IV. The Greek Church was excommunicated, and Charles was given renewed papal support for the invasion of Constantinople. In order to counter this, Michael VIII subsidized Peter III of Aragon's attempts to seize Sicily from Charles. Michael's efforts paid off with the outbreak of the Sicilian Vespers, a revolt that overthrew the Angevin King of Sicily and installed Peter III of Aragon as King of Sicily in 1281.