Martin Luther was responsible for sparking the Protestant Reformation through his opposition to the Catholic Church's practices. In 1517, Luther nailed his 95 Theses criticizing indulgences to a church door in Wittenberg, sparking debate across Europe. Though not intending revolution, Luther refused to retract his statements even when threatened. His ideas resonated with many who were discontent with the Church's corruption and desire for spiritual freedom. While inspired by earlier thinkers, Luther's influence grew the strongest and most threatening to the Pope, marking him as the leader of the Reformation.