The French Revolution began in 1789 as the oppressed Third Estate revolted against the feudal system and absolute monarchy of Louis XVI. They declared the National Assembly and stormed the Bastille, beginning the Revolution. The Revolution established France as a constitutional monarchy but growing radicalism led to the establishment of a republic and Reign of Terror under Robespierre. Napoleon later seized power and established an empire, conquering much of Europe, before his defeat at Waterloo. The Congress of Vienna established a balance of power and conservative order in post-Napoleonic Europe.