<P> France eventually issued an ultimatum demanding that the Habsburg Monarchy of Austria under Leopold II who also was Emperor of the Holy Roman Empire renounce any hostile alliances and withdraw its troops from the French border . The reply was evasive and the Assembly voted for war on 20 April 1792 against Francis II (who succeeded Leopold II), after a long list of grievances presented by foreign minister Dumouriez . Dumouriez prepared an immediate invasion of the Austrian Netherlands, where he expected the local population to rise against Austrian rule, as they had earlier in 1790 . However, the revolution had thoroughly disorganized the army, and the forces raised were insufficient for the invasion . Following the declaration of war, French soldiers deserted en masse and, in one case, murdered their general, Théobald Dillon . </P> <P> While the revolutionary government frantically raised fresh troops and reorganized its armies, a mostly Prussian Allied army under Charles William Ferdinand, Duke of Brunswick assembled at Koblenz on the Rhine . </P> <P> The duke then issued a proclamation called the Brunswick Manifesto (July 1792), written by the French king's cousin, Louis Joseph de Bourbon, Prince de Condé, the leader of an émigré corps within the Allied army, which declared the Allies' intent to restore the king to his full powers and to treat any person or town who opposed them as rebels to be condemned to death by martial law . This, however, had the effect of strengthening the resolve of the revolutionary army and government to oppose them by any means necessary . </P> <P> On 10 August, a crowd stormed the Tuileries Palace, seizing the king and his family . On 19 August 1792, the invasion by Brunswick's army commenced, with Brunswick's army easily taking the fortresses of Longwy and Verdun . </P>

Why did france and britain fight in the war