The siege of Valenciennes of 24 May-28 July 1793 was one of the last Allied successes in the campaign on the borders of France during the summer of 1793, but the slow pace of the siege gave the French time to recover from the disasters of the spring, and the year ended with a series of French victories. At the start of 1793 French armies under General Dumouriez invaded the Netherlands, but on 1 March the Austrians launched a counterattack, crossing the River Roer and defeating the French at Aldenhoven (1 March) and Aix-la-Chapelle (2 March). General Dumouriez had been forced to leave the army in Holland and move south in an attempt to restore the situation, but he was defeated at Neerwinden (18 March). Dumouriez was already out of step with the radical Jacobin elements in Paris, and after Neerwinden he began to plan for a march on Paris to restore order. On 4 April his army refused to support him, and on the following day Dumouriez went into exile with the Austrians.
In the aftermath of Dumouriez's defection the French were forced out of most of Belgium, and took up a defensive position along the French border. The Allies moved to besiege Condé-sur-l'Escaut. The new French commander, General Dampierre, was killed while attempting to lift this siege (battle of Condé or St Amand, 8 May 1793), and was replaced by General Custine. The French front line now ran through Valenciennes, which was defended by a strong camp at Famars, to the south of the city. On 23 May the Allies attacked this camp, and although their assault was largely unsuccessful, the French were forced to withdraw from this exposed position. That left the Allies free to begin a siege of Valenciennes itself.
Command of the besieging forces was offered to the Duke of York. The British Cabinet was concerned that this would prevent him from attacking Dunkirk, which was then the main British target, but eventually decided to accept the offer. The Duke was given command of the 25,000 men who actually conducted the siege, amongst them 14,000 Austrians and a large number of British troops, but Coburg also appointed General Ferraris to the duke's staff. Another 30,000 men formed a covering army.
Ferraris insisted on a slow regular siege, instead of the immediate assault favoured by the Duke's chief engineer, Colonel Moncrieff. The construction of the siege works progressed slowly. The main Allied attack was to be made on greater and lesser horn-works on the east side of the town, but the ground was not broken in front of these defences until 13 June. Over the next month tunnels were dug under the walls, and on the night of 25 July the mines were exploded. On the following day three columns attacked the two horn-works, and by the end of the day the Allies had gained a lodgement in the greater one.
On 26 July the Duke of York summoned the city to surrender, and announced that this would be the last such summons. General Ferrand asked for a twenty-four hour truce, and after negotiations the garrison surrendered. The French were allowed to march out of Valenciennes with honours of war, and were allowed to return home, as long as they agreed not to serve against the Allies for the rest of the war.
The Allies now separated, The British moved north to besiege Dunkirk, while the Austrians attacked Quesnoy and Maubeuge. The slow pace of the Allied campaign had given the French a chance to recover from the blows of the spring. Custine himself was removed from command, and executed on 18 August. He was replaced by General Jean Houchard, who despite defeating the British at Hondschoote and the Dutch at Menin was himself soon executed. Finally General Jean-Baptiste Jourdan was given the command, and defeated the Austrians at Wattignies (15-16 October 1793). By the end of the year the French were once again in the ascendency.