Martin Luther, a former Catholic priest, sparked the Protestant Reformation in 1517 when he posted his 95 Theses criticizing corrupt Catholic practices like indulgences. When his views were deemed heretical, he was excommunicated by the Pope but gained support of German princes. Ulrich Zwingli also preached reform in Switzerland, arguing for a break from Catholicism. John Calvin further developed Protestant theology, believing in predestination. Meanwhile, King Henry VIII separated England from Rome when the Pope refused to annul his marriage, establishing the Church of England with himself as its head and executing those who remained Catholic. The Reformation challenged Catholic unity but also sparked reforms through the Counter-Reformation and Vatican II