The battle of Le Boulou (30 April-1 May 1794) was a French victory in the eastern Pyrenees that forced the Spanish to retreat back across the border a year after they had first crossed into France. After a series of early successes that saw them come close to Perpignan the Spanish had pulled back to the Tech River, just to the north of the Pyrenees, and by the winter of 1793-94 their left was at Ceret (with detachments in the Vallespir, further up the valley), their centre was at Le Boulou and their right was on the coast, between Argelès-sur-Mer and Banyuls-sur-Mer.
Both armies had new commanders at the start of the 1794 campaign. The Spanish commander in 1793, General Ricardós, had died while visiting Madrid. His replacement, General O'Reilly, had died on his way to the army. His chosen replacement, the Comte de La Union, turned down the post three times, and for some time the army was commandeered by the Marquis de Las-Amarillas, but by the end of April La Union had finally taken up his new post.
The change on the French side was more positive. In January 1794 General Dugommier, the conqueror of Toulon, took command of the Army of the Eastern Pyrenees, bringing with him 10,000 experienced troops. Over the next three months he reorganised and trained his army, and by the spring it was a much more effective force than in 1793.
Dugommier decided to make a feint towards Ceret, to convince the Spanish that he was about to attack their left, but then make his real attack between the Spanish centre and right. The camp at Le Boulou was well fortified. Its right flank was protected by two redoubts – La Trompette and Montequiou - but the Spanish had not fortified the mountains behind their line. Dugommier's plan was to cross the Tech to the east of the redoubts, climb the mountains, and attack the Spanish centre from the rear.
In the days before the main attack General Augereau, with the French right, was sent towards Ceret. La Union fell for the French trap, and concentrated his army on his left, leaving the Le Boulou comparatively weakly defended.
The main attack began on the night of 29-30 April when General Pérignon crossed the Tech using the ford of Brouilla. His force was split into four columns. One, under General Martin, captured the position on the mountains. Martin then sent Adjutant General Frère with 800 men to attack La Trompette. The other three advanced towards Saint-Genis and Villelongue. Victor faced east, to watch the Spanish right, while the rest of his force turned west. By dawn Pérignon's main force was drawn up in order of battle facing west towards the Spanish camp.
When the sound of French gunfire reached La Union at Ceret he sent the Prince de Montforte east with a few battalions, missing his best chance to defeat the French attack. If La Union had rushed every available solder east then he might have been able to trap the French against the river or the mountains before they were fully established across the Tech, but Montforte's small force was able to achieve very little. The Count del Puerto, with two battalions and a regiment of dragoons, was sent to help Venegas, who was under attack in the redoubt of Montesquiou. Venegas was wounded in the fighting, and was forced to retreat to the signal battery, close to the main camp. Overnight the Spanish were also forced to evacuate La Trompette.
That night the Spanish held a council of war. Not only had the French captured the two main redoubts defending the camp at La Boulou, they had also advanced across the mountains onto the main road from La Boulou back into Spain, blocking the road that ran past the fort of Bellegarde. The only escape routes left to the Spanish were the obscure Col de Porteil (not to be found on modern maps, Porteil may simply be the local name for a pass across. The Spanish escape route took then up the heights of Maureillas, so the pass may be the Col de Figuier, crossing the mountains at Las Illas). Given these circumstances it was inevitable that the council of war decided to retreat.
The Spanish retreat quickly turned into a rout. At dawn on 1 May General Pérignon attacked and captured the Signal battery, and completed the defeat of what had become the Spanish right. Montforte attempted to retreat towards Bellegarde, but found his way blocked at the village of Les Cluses and was forced to join the centre on the heights of Maureillas. Pérignon sent his cavalry along the south bank of the Tech to harry the Spanish retreat, and the Spanish generals were unable to restore order. The men became tangled in the retreating baggage and artillery, especially after Augereau crossed the bridge at Ceret. By the end of the day the French had captured 1,500 prisoners, 150 guns, 800 mules and the entire baggage of the army.
The collapse of the Spanish centre forced them to pull back on both flanks. On the coast they abandoned Argèles but kept Collioure and Port-Vendres. Their line then ran along the top of the mountains to Bellegarde, which remained in their hands. The left retreated from the Vallespir to Sant Llorenç de la Muga (due south of Ceret on the southern side of the mountains). The main Spanish army took up a new position under the guns of Figueres.
Bellegarde would soon be besieged by the French, but Dugommier spent the rest of the summer besieging the coastal ports that had remained in Spanish hands, while Bellegarde itself didn't fall until mid-September.