True. The Thirty Years' War was a conflict fought between 1618 and 1648 primarily in Central Europe. It began as a religious war between Protestants and Catholics in the Holy Roman Empire but eventually spread to involve most of the major European powers. While the war had political and economic motivations as well, religion played a significant role in its origins and the loyalties of the various factions involved. The war ultimately ended with the Peace of Westphalia in 1648, which marked a significant shift towards secularism in European politics and diplomacy.