The Declaration united the French people against its authors. The Republicans whom it threatened and denounced became the appointed leaders of the national defence, and the cause of the Republic became identified with the safety of the nation. In order to withstand the invasion, and to preserve Paris from the fate of Jerusalem, the army gave itself to the dominant faction. The royalist element vanished from its ranks. Lafayette made one last attempt to uphold the Constitution, but his men repulsed him. He went over to imperial territory, and was detained in prison as the guilty author of the Revolution. Dumouriez succeeded to his command, and adhered to the new government. Out of 9000 officers in the king's service, 6000 had resigned, and, for the most part, had emigrated. Their places were filled by new men. In 1791, 100,000 volunteers had been enrolled, and enjoyed the privilege of electing their own officers. This became the popular force, and recruits preferred it to the line, where discipline was sterner and elected commanders were unknown. The men who now rose from the ranks proved better professional soldiers than the fine gentlemen whom they replaced. Talent could not fail to make its way. Those volunteer officers of 1791 and 1792 included most of the men whom the long war raised to eminence. Seventeen of the twenty-six marshals of Napoleon were among them.
On the 19th of August, four months after war had been declared, the allies entered France by the line of the Moselle. There was one French army to their left at Metz, and another to their right along Vauban's chain of fortresses, with an undefended interval between. To widen the gap they laid siege to Longwy, the nearest fortified place, and took it, after a feeble resistance, on August 24. When the news spread there was a moment of alarm, and the Council of Defence proposed to retire from the capital. Danton declared that he would burn Paris to the ground rather than abandon it to the enemy. Lavergne, who made so poor a defence at Longwy, was afterwards condemned to death. He was disheartened by disaster, but his wife cried out that she would perish with him, and the judges granted her prayer. She strove to give him comfort and courage along the way, and they were guillotined together.
From Longwy the Prussians advanced upon Verdun, which surrendered September 2, after one day's bombardment, and there was not a rampart between them and the capital. A few miles beyond Verdun the roads to the west traversed the Argonne, a low wooded range of hills pierced in five places by narrow defiles, easy to defend. Then came the open country of Champagne, and the valley of the Marne, leading, without a natural or artificial obstacle, to Paris.
On the 7th of September Pitt wrote that he expected Brunswick soon to reach his goal. There was no enemy in his front, while on his flank Dumouriez clung to his frontier strongholds, persuaded that he would arrest the invasion if he threatened the Austrians at Brussels, where they were weakened by recent insurrection and civil war. The French government rejected his audacious project, and ordered him to move on Châlons, and cover the heart of France. At Sedan, Dumouriez could hear heavy firing at a distance, and knew that Verdun was attacked, and could not hold out. He quickly changed his plan, postponing Belgium, but not for long, and fell back on the passes of the forest that he was about to make so famous. "They are the Thermopylæ of France," he said, "but I mean to do better than Leonidas."
Brunswick, delaying his cumbrous march for ten days, while Breteuil organised a new administration at Verdun, gave time for the French to strengthen their position. Before moving forward, he pointed out on the map the place where he intended to halt on the 16th, and men heard for the first time the historic name, Valmy. On the 14th Clerfayt, with the Austrians, forced one of the passes, and turned the French left. At nightfall, Dumouriez evacuated his Thermopylæ more expeditiously than became a rival Leonidas, and established himself across the great road to Châlons, opposite the southern defile of the Argonne, which extends between Clermont and St. Ménehould, where Drouet rode in pursuit of the king. His infantry encountered Prussian troopers and ran away. Ten thousand men, he wrote, were put to flight by fifteen hundred hussars.
Napoleon said, at St. Helena, that he believed himself to be bolder than any general that ever lived, but he would never have dared to hold the position that Dumouriez took up. He was outnumbered, three to one. He had been outmanœuvred, and driven from his fastness by the most enterprising of the allied generals; and his recruits refused to face the enemy. He never for a moment lost confidence in himself, for the time wasted at Verdun had given him the measure of his opponents. He summoned Kellermann, with the army of Metz, and Beurnonville, with 10,000 men, from Lille, and they arrived, just in time, on the 19th. Beurnonville, when his telescope showed him a regular army in order of battle, took alarm and fell back, thinking it must be Brunswick. It proved to be Dumouriez; and on the morning of September 20 he was at the head of 53,000 men, with the allies gathering in his front. The Prussians had come through the woods by the pass he had abandoned, and as they turned to face him, they stood with their backs to the great Catalaunian plain, which was traversed by the high road to Paris. They had been for a month in France, and had met with no resistance. Lafayette had deserted. The military breakdown was so apparent that the colonel of infantry, as he marched out of Longwy, threw himself into the river, and the governor of Verdun blew out his brains.
Clerfayt's success on the 14th and the rout of the following day raised the hopes of the Germans, and they wrote on the 19th that they were turning the enemy, and were sure of destroying him, if he was rash enough to wait their attack. From his prison at Luxemburg Lafayette urged them onward, and hinted that Dumouriez might be induced to unite with them for the rescue of the king.
Therefore, on the morning of September 20, when the mist rose over the French army drawn up on the low hills before them, there was joy in the Prussian camp, and the battalions that had been trained at Potsdam, under the eye of the great king, to the admiration of Europe, received for the first time the republican fire. They were 34,000. Kellermann opposed them with 36,000 men, and 40 guns against 58. It soon appeared that things were not going as the invaders had expected. The French soldiers were not frightened by the cannonade. Beurnonville rode up to one of his regiments and told them to lie down, to make way for shot. They refused to obey whilst he exposed himself on horseback. After time had been allowed for artillery to produce its effect on republican nerve, the Prussian infantry made ready to attack. Gouvion St. Cyr, the only general of his time whom Napoleon acknowledged as his equal, believed that the French would not have stood at close quarters. But the word to advance was never given.
The secret of war, said Wellington, is to find out what is going on on the other side of the hill. When Brunswick rode over the field some days later, a staff officer asked him why he had not moved forward. He answered, "Because I did not know what was behind the hill." There was Dumouriez's reserve of 16,000 men. He had sent to the front as many as were needed to fill Kellermann's line, and left to his colleague the part for which he was fitted. For his conduct that day Kellermann was named a marshal of the Empire and duke of Valmy; but the whole world was aware that the event was due to the brain of the man in the background. When the French had lost 300 men without wavering, the Prussians ceased firing, and broke off the engagement. Their loss was only 184. Yet this third-rate and mediocre action is counted, with Waterloo and Gettysburg, among the decisive battles of history; and Goethe was not the only man there who knew that the scene before him was the beginning of a new epoch for mankind. With 36,000 men and 40 guns the French had arrested the advance of Europe, not by skilful tactics or the touch of steel, but by the moral effect of their solidity when they met the best of existing armies. The nation discovered that the Continent was at its mercy, and the war begun for the salvation of monarchy became a war for the expansion of the Republic. It was founded at Paris, and consolidated at Valmy. Yet no military event was less decisive. The French stood their ground because nobody attacked them, and they were not attacked because they stood their ground. The Prussians suffered a strategic, though not a tactical defeat. By retiring to their encampment they renounced the purposes for which they went to war, the province they occupied, and the prestige of Frederic. They no longer possessed the advantage of numbers, and without superior numbers there could be no dash for Paris.