The war began with a gesture of theological theatre: on 23 May 1618 Protestant nobles threw two Catholic regents and their secretary from a window of Prague Castle, and the men's survival was claimed by one side as angelic rescue and by the other as a soft landing. The Bohemian revolt against the Habsburg emperor drew in the Protestant princes of the Empire and was crushed at the White Mountain in 1620, but the war refused to end: Denmark entered and was beaten, the emperor's Edict of Restitution of 1629 tried to reclaim a century of secularised church lands and frightened even his allies, and in 1630 Gustavus Adolphus of Sweden landed as the armed champion of Protestantism, winning at Breitenfeld and dying at Lutzen in 1632.
The war's last and longest phase stripped its confessional logic bare: Catholic France, governed by a cardinal, financed and then joined the Protestant side against the Catholic Habsburgs, and the fighting ground on for sixteen more years as armies that no one could pay lived off a devastated land. Peter Wilson's standard history reckons the German lands lost around a fifth of their population, some five million people, to violence, famine and plague, proportionally the worst catastrophe in German history.
The Peace of Westphalia, negotiated in parallel congresses at Munster and Osnabruck and signed in 1648, ended the war and rebuilt the Empire's religious constitution on a basis that would hold for a century and a half.