In the spring of 1792, France declared war on Austria and Prussia. This decision followed a series of diplomatic tensions that had been building since the French Revolution began in 1789. The other monarchies of Europe watched with outrage as their neighbor transformed into a republic. Holy Roman Emperor Leopold II issued the Declaration of Pillnitz on the 27th of August 1791 alongside King Frederick William II of Prussia. They threatened severe consequences if anything happened to King Louis XVI and Queen Marie Antoinette. France viewed this declaration as a serious threat despite Leopold's intention to placate French monarchists. The Legislative Assembly voted for war on the 20th of April 1792 after foreign minister Charles François Dumouriez presented a long list of grievances. French soldiers deserted en masse following the declaration. In one case, they murdered their general, Théobald Dillon. A mostly Prussian allied army under Charles William Ferdinand, Duke of Brunswick assembled at Koblenz on the Rhine. The duke issued the Brunswick Manifesto in July 1792, which declared the allies' intent to restore the king to his full powers. Any person or town opposing them would be condemned to death by martial law. On the 20th of September, invaders came to a stalemate against Dumouriez and Kellermann at the Battle of Valmy. The highly professional French artillery distinguished itself during this tactical draw. The Prussians decided that the cost and risk of continued fighting was too great with winter approaching. They retreated from France to preserve their army.
First Coalition Campaigns
A series of victories by the French Revolutionary Army abruptly ended with defeat at Neerwinden in the spring of 1793. The French suffered additional defeats in the remainder of the year, allowing the Jacobins to rise to power and impose the Reign of Terror to unify the nation. Spain and Portugal entered the anti-French coalition in January 1793. Britain began military preparations in late 1792 and declared war inevitable unless France gave up its conquests. France responded by declaring war on Great Britain and the Dutch Republic on the 1st of February. France drafted hundreds of thousands of men beginning a policy of using mass conscription to deploy more manpower than autocratic states could manage. A decree of the 24th of February 1793 ordered the draft of 300,000 men followed by general mobilization through the famous decree of the 23rd of August 1793. By 1795, the French had captured the Austrian Netherlands and the Dutch Republic. The French also put Spain and Prussia out of the war with the Peace of Basel. An unknown young artillery officer named Napoleon Bonaparte contributed to the siege of Toulon by planning an effective assault with well-placed artillery batteries. This performance helped make his reputation as a capable tactician and fueled his meteoric rise to military and political power. In 1794, huge victories at Fleurus against the Austrians and Dutch and against the Spanish at the Battle of the Black Mountain signaled the start of a new stage in the wars.