The Thirty Years’ War was one of the largest, most devastating wars in European history involving (among others) the Holy Roman Empire, the Spanish Empire, Denmark-Norway, the Swedish Empire, the Kingdom of Bohemia, the Dutch Republic, and the Kingdom of France. There were many different causes for this pan-European conflict, but perhaps the most prominent was the Reformation sweeping across the continent. There were no clear victors, but the conflict had far-reaching consequences for the future of Europe as it dramatically shifted the balance of power and consolidated Protestantism.

While fought for several reasons, the war is widely seen to have been triggered by an attempt in 1681 by the King of Bohemia, the future Holy Roman Emperor Ferdinand II, to impose Catholicism where he ruled. When protestant nobles rebelled, fights broke out across Europe. When the Treaty of Westphalia was signed in 1648, the Netherlands were made independent from Spain, Sweden took control of the Baltic, and France stood strong as a main power in the West. The Holy Roman Empire, however, was broken, as German states again could choose their own religion. Following the treaty, the principle of state sovereignty emerged, providing the foundation for the idea of the nation-state.