The Thirty Years' War was a series of conflicts in Europe from 1618 to 1648, primarily fought in the Holy Roman Empire. It began as a struggle between Catholic and Protestant states but evolved into a broader political conflict involving major powers like France, Sweden, and Spain. The war caused widespread destruction and significant loss of life. The conflict ended with the Peace of Westphalia in 1648, which established a new political order in Europe. This treaty recognized the sovereignty of various states and laid the groundwork for modern international relations, marking a shift towards state-based diplomacy.