Pope Leo X, tired of Martin Luther's constant criticism, finally had enough! On January 3, 1521, he issued the papal bull Decet Romanum Pontificem, excommunicating the rebellious German theologian. This was the ultimate spiritual penalty, kicking Luther out of the Catholic Church! The Pope's decree was the culmination of a decades-long struggle between the Church and Luther, who dared to challenge its authority. This bold move sparked a chain reaction, shaping the course of Christianity and cementing the Protestant Reformation.