Meanwhile, three armies were invading France, two Austrians and one Prussian: Longwy first, Verdun later fell into the hands of the Prussians, Thionville into the hands of the Austrians. The predominantly Girondist ministry, which had assumed power after 10 August, wanted to move the capital elsewhere, but Danton, who covered the department of Justice in the same ministry, opposed with his overwhelming energy (28 August) and, if not he ordered, certainly prepared with his political conception and consecrated, assuming responsibility, those terrible massacres of September (2-6 September), which horrified all civilized Europe. While the revolution carried out its massacres on the inside, on the outside it achieved its first victory: in Valmy, on 20 September 1792, for the first time the troops of the revolution did not turn their backs on the enemy.
According to mathgeneral, the Convention was inaugurated on 21 September among the most brilliant military successes: while Dumouriez won in Valmy, General Montesquiou conquered Savoy, General Anselme entered Nice and General Custine in Spira (30 September) and Mainz (21 October). The assembly was divided between the Gironde and the Mountain, which were political tendencies rather than parties in the exact sense of the word, of which the one wanted to maintain the normal course of the administration of justice and economic freedom, and the other wanted measures of exception. Danton tried to put a bridge between the two sides: no agrarian law and no dictatorship, therefore the Gironde was happy; no federalism, therefore the Montagna is happy, all united in frankly consolidating a unitary democratic republic. The republic was proclaimed on 21 September itself, thanks to the tact of Danton, who managed to obtain a truce between the two sides; but the Gironde immediately launched a deadly offensive against the Mountain: in Danton, who had left the Ministry of Justice, the accounts of his administration were asked, Marat and Robespierre were denounced for their dictatorial aims, a departmental guard was invoked to defend the Convention from pressure from the people of Paris. The majority of the assembly, hitherto fluctuating, opposed these measures, and the Montagna was able to go on the counterattack, asking for the king’s trial. The Girondins tried to extend it and save the king’s life, but dragged by the majority of the chamber, they capitulated and the king was guillotined on January 21, 1793. The European public opinion was moved by this crime: England, Spain, the small Italian and Germanic powers broke off relations with France. Then the first coalition was formed, animated by England, which had clearly sided with the enemies of France, ever since the Dumouriez had conquered Belgium after the beautiful victory of Jemappes (6 November), and the mouths of the Scheldt (November 16) against the Treaty of Westphalia. Burke, the animator of the counter-revolutionary action, would have liked a war of principles to be set up: not France was being fought, but the revolution, and it was necessary to support the realist party in France and not think about conquering colonies or financial or territorial indemnities.. But Pitt remained in the diplomatic field and wanted only to impose on France the respect of international treaties and the principle of balance. This prevented the counter-revolutionary war from having that ethical-religious inspiration, which the revolutionary war had in Girondist thought.
While the European powers showed themselves so not very energetic and shrewd in not clearly bringing the war to the moral ground, two principles were inserted in the incipient revolutionary diplomacy which in a new rhetorical language continued old, glorious and skilful traditions: the principle of bringing aid the use of the concepts of “freedom of Italy, of Germany, of Europe”, of the deeds of Gods for Francos continued to all slave peopleshad made the old monarchy, and the principle of natural borders, to the Alps and the Rhine: the two concepts, supported in particular by the Girondists, the other by Danton, integrated and ensured that France, while serving the cause of civilization, did not forget itself. On the basis of the principle of natural borders and the self-decision or spontaneous dedication of peoples, Savoy (27 November), Nice (31 January 1793), Belgium and the Rhineland (March) were annexed to France.
Encouraged by its success, the Convention had Dumouriez invade Holland (February 26), but the Austrians, led by the Prince of Coburg, invaded Belgium and beat Dumouriez, who returned to defend him, at Neerwinden on March 18, reconquered Belgium, entered in France, and began the siege of the fortresses created by Vauban in the north of France. Meanwhile the Sardinians reoccupied Savoy, and the Spaniards, led by Ricardos and Caro, entered France. The Vendée, already excited by refractory priests, rebelled against conscription (10-15 March). The people in the cities called for or imposed the regulation of economic life. The peasants wanted to put an end to the land problem for good. The moment was very serious. The Mountain felt its hour had come and promoted the institution of a Public Health Committee which Danton joined (April 5-6). The Girondists tried to prevent it with a header. On 1 April they accused Danton of treason, on 13 they railed against Marat, Hébert and Robespierre as aspirants to the dictatorship. But the Mountain, backed by the revolutionary sections of Paris, forced the Convention to arrest 29 Girondins (May 31-June 2). The Mountain thus finally reached power and held it with an iron fist. The new constitution, founded on universal suffrage, was proclaimed on June 24 and this juridically satisfied the extremist currents.