The primary cause of the Thirty Years' War in Europe was religious conflict, primarily between Catholics and Protestants within the Holy Roman Empire. The war began in 1618 when a Protestant uprising against Catholic rule in Bohemia escalated into a broader conflict involving various European powers. Issues of political power, territorial disputes, and the desire for dominance among nations also fueled the war. The conflict became one of the most destructive in European history, leading to significant loss of life, economic hardship, and the eventual Peace of Westphalia in 1648, which established a new political order based on state sovereignty.