On the morning of 23 May 1618, a delegation of Protestant Bohemian nobles led by Count Heinrich Matthias Thurn climbed the stairs of Prague Castle to confront the two Catholic regents — Vilém Slavata and Jaroslav Bořita of Martinice — who had been administering Bohemia for the absent Habsburg Emperor Matthias. The delegation had a substantial list of grievances: violations of the 1609 Letter of Majesty (which guaranteed Bohemian Protestant religious rights), Catholic interference with Protestant church construction, and broader Habsburg-Catholic intent to reverse the substantial Bohemian Protestant settlement of the previous century.
The confrontation in the chancery of the Bohemian Chancellery escalated quickly. The Protestant delegation declared the two regents personally responsible for the violations. Slavata and Martinice denied jurisdiction. The delegation seized them and the regents’ secretary Filip Fabricius, dragged them to the window of the third-storey chancery chamber, and threw all three out.
The fall
The window stood approximately 21 metres above the dry castle ditch below. The fall should have killed the three men. None of them died. Slavata broke an arm and received substantial cuts; Martinice was uninjured; Fabricius was bruised but able to walk away.
The survival has had two competing explanations. The Catholic-providential version: the Virgin Mary substantively caught the three men as they fell and lowered them gently to the ground. Fabricius was subsequently ennobled by the Emperor with the surname von Hohenfall (‘of the High Fall’) in commemoration. The naturalistic version: the castle ditch had been used as a refuse-and-dung dump for decades; the three men landed in a deep pile of soft animal manure that absorbed the impact.
The dung version is the standing modern historical consensus.
What it started
The Defenestration triggered the Bohemian Revolt of 1618–1620 — Protestant Bohemian forces drove out the Habsburg administration, elected the Calvinist Frederick V of the Palatinate as ‘Winter King’, and established an independent Bohemian Protestant state. The Habsburg-Catholic counter-attack came at the Battle of White Mountain outside Prague on 8 November 1620. The Bohemian Protestant army was destroyed in approximately two hours. Catholic Habsburg control was restored; the Bohemian Protestant nobility was executed, exiled, or dispossessed; Bohemia was forcibly re-Catholicised over the following decade.
The wider European war the Defenestration had triggered continued until the Peace of Westphalia in 1648 — thirty years that killed perhaps eight million people across central Europe.