The battle of Avesnes-le-Sec (12 September 1793) saw a sizable French infantry column virtually destroyed by an Austrian cavalry attack, and demonstrated that the new conscripted French infantry could still be vulnerable. The disaster also proved that revolutionary enthusiasm was no substitute for military ability, and was largly the fault of Nicholas Declaye, the military commander at Cambrai.
Cambrai had very briefly been besieged by the Austrians, but that attack was abandoned on 11 August, and the Prince of Saxe-Coburg moved east to attack La Quesnoy. General Houchard, the French commander in the north, was under great pressure to save the town, but was not really in a position to make a serious attempt to do so. Instead he decided to make two feints against Austrian positions, one from Maubeuge, and one from Cambrai against the Austrian camp at Solesmes. Unfortunately no detailed orders for these attacks were issued, and Declaye does not seem to have realised that he was not actually meant to attack Solesmes. Before leaving Cambrai he announced to the city authorities that he would not return until he had won a complete victory over the Austrians.
Declaye left Cambrai at one o'clock in the morning of 12 September, at the head of 2,500 infantry, 240 cavalry and 120 gunners. Two hours later the column reached Bouchain, where it was joined by 1,300 men from the garrison, amongst them some of the gunners. This gave Declaye 4,160 men, most of them infantry.
When he learnt that a French column had left Cambrai, the Allied commander-in-chief, the Prince of Saxe-Coburg, ordered the Prince of Hohenlohe-Kirchberg to take a small force against it. Hohenlohe-Kirchberg was given three infantry battalions and two squadrons from the Nassau regiment of Cuirassiers. He was supported by the prince of Lichtenstein, with the Kinsky Cheveuxlegers (light cavalry) and five companies of infantry, from the camp at Saulzoir. The force also included three squadrons of Imperial Hussars from Solesmes and one squadron of French exiles from the guard cavalry corps of Royal-Allemand. Only the cavalry, about 2,000 strong, would actually take part in the fighting at Avesnes-le-Sec.
The French column advanced north east from Cambrai to Avesnes-le-Sec, driving away a number of Austrian patrols, then turned left to head south east, towards Villers-en-Cauchies. Instead of stopping there, Declaye continued on south-east, towards the Austrian camp at Solesmes. As the French column was passing Villers, the Austrian cavalry appeared on the hills to the left of the road.
When he saw this large cavalry force, Declaye ordered his column to retreat back to Avesnes-le-Sec, leaving his cavalry to hold off the Austrians. Hohenlohe responded to the French retreat by ordering a cavalry charge, and outnumbered by nearly ten-to-one the French cavalry broke and fled. Declaye's actions at this stage are unclear. He claimed that he followed the cavalry in an attempt to rally it, but he was probably caught up in their rout. The cavalry reached safety at Bouchain at about ten in the morning.
The French infantry, abandoned by the cavalry, reached Avesnes-le-Sec, and formed into two squares just south of the village, with the cannons in the gap between the squares. The Austrians surrounded the French squares on three sides, with the Imperial Hussars to the right, the Nassau Cuiraissiers and the Royal-Allamand to the left and the Kinsky Cheveuxlegers to the front. Normally infantry squares were almost impervious to unsupported cavalry attacks, but that was only the case with well trained infantry. Like most French armies of this period Declaye's infantry had contained a mix of regulars and the new Revolutionary volunteers and conscripts. When the cavalry charged, the French squares were broken, and a dreadful slaughter followed. Some of the infantry attempted to escape through Avesnes-le-Sec, but Coburg, who had just arrived on the scene, sent some of his cavalry around the village to block their escape. Eventually the French lost 2,000 dead and 2,000 prisoners, as well as 3,000 muskets, 20 guns and 3 flags. The Austrians only suffered 69 casualties.
The first survivors from the disaster reached Cambrai before noon, soon after news of the French victory at Hondschoote. At first the townsmen refused to believe the news, but as more of the cavalry reached Cambrai it became clear that the French had suffered a bad defeat. At three in the afternoon Marceaux, a member of the local committee who had accompanied the army, arrived, and reported that Declaye had abandoned the army at the first shock, and had fled with the cavalry, but confirmed that the infantry had fought to the last. Declaye himself finally arrived at eight in the evening, with two or three hundred survivors.
Over the next few days Declaye's conduct came under scrutiny, and he came close to being sent to Paris for trial as a traitor. At first he tried to play down the scale of the disaster, claiming that his army was smaller than stated but eventually he was forced to admit to the real scale of the loses. Fortunately for Declaye, he was well known as a sans-culotte and a zelous revolutionary, and was a friend of the head of the secret police. Eventually it was decided that he was simply incompetent, and he was moved to a less important post at Lyon, a rare example of a French military commander of this period surviving such a disastrous defeat. The entire expedition had been a wasted effort anyway, for Le Quesnoy surrendered on 11 September, the day before it began.