In April 1792, the newly elected Legislative Assembly declared war on Austria and Prussia, where it believed that French émigrés were building counterrevolutionary alliances; it also hoped to spread its revolutionary ideals across Europe through warfare. On the domestic front, meanwhile, the political crisis took a radical turn when a group of insurgents led by the extremist Jacobins attacked the royal residence in Paris and arrested the king on August 10, 1792. The following month, amid a wave of violence in which Parisian insurrectionists massacred hundreds of accused counterrevolutionaries, the Legislative Assembly was replaced by the National Convention, which proclaimed the abolition of the monarchy and the establishment of the French republic. On January 21, 1793, it sent King Louis XVI, condemned to death for high treason and crimes against the state, to the guillotine; his wife Marie-Antoinette (1755-1793) suffered the same fate nine months later.
Following the king’s execution, war with various European powers and intense divisions within the National Convention ushered the French Revolution into its most violent and turbulent phase. In June 1793, the Jacobins seized control of the National Convention from the more moderate Girondins and instituted a series of radical measures, including the establishment of a new calendar and the eradication of Christianity. They also unleashed the bloody Reign of Terror (“la Terreur”), a 10-month period in which suspected enemies of the revolution were guillotined by the thousands. Many of the killings were carried out under orders from Robespierre, who dominated the draconian Committee of Public Safety until his own execution on July 28, 1794. His death marked the beginning of the Thermidorian Reaction, a moderate phase in which the French people revolted against the Reign of Terror’s excesses.