When Martin Luther nailed his Ninety-Five Theses to the church door in Wittenberg, he did more than challenge ecclesiastical corruption—he ignited a revolution that transformed the foundations of European power. The Reformation was not a single act of protest but a century-long conflict over belief, authority, and the right to interpret truth. This book traces the ripple of Luther's defiance across Europe: from the German principalities to Calvin's Geneva, from Henry VIII's England to the wars that tore the continent apart. Drawing on letters, sermons, and court records, it follows how theology met politics—how kings and peasants alike seized scripture as a weapon of justification. The printing press turned ideas into armies; sermons turned faith into rebellion. Through analysis of doctrine, propaganda, and institutional response, the narrative illuminates how a theological dispute reshaped art, governance, and conscience. What began with one monk's protest became the crucible in which modern Europe—and the modern notion of individual belief—was forged.