The French king was put under surveillance, and increasingly suspected of conspiring with other European monarchs, who wished to preserve the House of Bourbon in France and restore its pre-revolutionary authority.

[1] Leading radical revolutionaries called for the complete abolition of the monarchy, but the republican movement was dealt a severe blow in the July 1791 Champs de Mars Massacre.

In early 1792, conservative royalist Armées des Émigrés were forming just across the borders in cities such as Koblenz, readying themselves to invade and end the Revolution with the help of other monarchies.

The Girondin majority in the Legislative Assembly favoured war, especially with Austria, in order to display the Revolution's strength and defend its achievements (such as the Declaration of the Rights of the Man and of the Citizen of 1789 and the early beginnings of parliamentary democracy) against a possible return to an (Enlightened) absolutist regime.

Major-general Charles François Dumouriez was appointed Minister of Foreign Affairs in March 1792, and by mid-April had managed to obtain the neutrality of all European great powers except Austria and Prussia through diplomacy.

[6] The invasion heavily relied on the presumption that Belgian and Liégois patriotic rebellions would break out spontaneously the moment French troops crossed the border, aiding them in driving out the Habsburg forces as they had done themselves 2.5 years before.

Dumouriez assured his fellow ministers:[8] As soon as the French army enters the Belgian provinces, it will be helped by the people, who are ashamed of their own futile revolutionary efforts of [1789–1790].

For the Country of Liège, the one most worthy of freedom of all those who have raised its flag, our negotiators will depart to dictate a wise peace, which we will under no circumstances spoil by the spirit of conquest.The French army was plagued by troubles: leading generals such as Lafayette and Rochambeau were moderate royalists, and had doubts about the republican minister's intentions as well as the feasibility of his strategies; the troops were poorly equipped, many of them untrained volunteers, and they distrusted their aristocratic officers; and finally, queen Marie Antoinette, who was Austrian and feared further republican radicalisation would result in her execution, secretly passed war plans to the Austrian government in Brussels, with Louis XVI's approval.

At the Battle of Marquain near Tournai (29 April), French soldiers fled almost at first sight of the Austrian outposts and murdered their general Théobald Dillon, whom they accused of treason.

[citation needed] Observing the enemy coalition gathering at its borders, the Assembly declared the 'nation in danger', and commanded 100,000 National Guards (Fédérés) to strengthen the defence of Paris; the king vetoed the decision, but he was ignored.

It was issued against the advice of Brunswick himself, whose signature appeared on it; the duke, a model sovereign in his own principality, sympathised with the constitutional side of the French Revolution, while as a soldier he had no confidence in the success of the enterprise.

Instead of intimidating the Parisians, it confirmed their determinacy to oppose any foreign invasion, and to get rid of the royals who were increasingly, and with ever more evidence, suspected of treason against the Revolution, the Assembly and the French people.

[13] With the imminent invasion of the allied European monarchies against it, radical revolutionaries in Paris could no longer tolerate the king's rule, as his foreign friends might soon restore his former powers and crush the Revolution.

In the night of 9 to 10 August, the insurrectional Paris Commune was formed at the Hôtel de Ville under the leadership of Georges Danton, Camille Desmoulins and Jacques Hébert from the ranks of radical Jacobins, the sans-culottes and a patriot regiment from Marsaille.

In a complicated series of actions by various groups, king Louis was isolated within his Tuileries Palace and gradually abandoned its defence until he and the royal family left it when Roederer persuaded him to seek 'safety' in the building of the Legislative Assembly instead.

But Dumouriez, who had been training his raw troops at Valenciennes in constant small engagements, with the purpose of invading Belgium, now threw himself into the Argonne by a rapid and daring flank march, almost under the eyes of the Prussian advance guard.

Dumouriez, undaunted, changed front so as to face north, with his right wing on the Argonne and his left stretching towards Châlons (where Luckner camped[15]), and in this position Kellermann joined him at Sainte-Menehould on 19 September 1792.

[15] At the moment when the Prussian manoeuvre was nearly completed, Kellermann, commanding in Dumouriez's momentary absence, advanced his left wing and took up a position between Sainte-Menehould and Valmy.

Dumouriez did not press the pursuit seriously; he occupied himself chiefly with a series of subtle and curious negotiations which, with the general advance of the French troops, brought about the complete withdrawal of the enemy from the soil of France.

Another French success was the daring expedition from Alsace into Germany made by Custine, leading the newly created 14,300 strong Armée des Vosges from 19 September onward.