The Combat of Mas-d'Ru (19 May 1793) was an early Spanish victory during the War of the Convention that saw them defeat a French force that was attempting to defend a position seven miles to the south-west of Perpignan. The War of the Convention began with a French declaration of war (7 March 1793), but it was the Spaniards who moved first. In April a small army under General Ricardós crossed the eastern Pyrenees, and on 20 April drove the French out of the town of Ceret on the Tech River. He then paused to wait for reinforcements, and didn't move again until mid May, by which time he had 18,000 men.
After the Spanish invasion the French Committee of Public Safety decided to split their Army of the Pyrenees in two. General Flers was given command of the Army of the Eastern Pyrenees, and ordered him to defend Perpignan. Flers had very few troops under his command, and many of them were new recruits. Flers decided to post his best troops – five infantry battalions and 400 cavalry under General Dagobert – seven miles to the south-west of the city, between the River Reart and a farm called Mas-d'Eu (now Mas Déu). The front of this line was protected by a ravine.
Ricardós was ready to move in mid-May. On the night of 18-19 May he advanced in four columns from Ceret towards Thuir, just to the west of the French position. Ricardós planned to turn the right of the French position. The Duke d'Ossun, on the Spanish left, was to make the turning movement, while General Courten attacked the right of the French position and General Villalbe attacked the centre.
Dagobert was in a strong position. Courten and Villalbe ran into heavy French artillery fire, which threatened to cause chaos in their army. Ricardós responded by sending his cavalry to his left, to attack the right of the French guns. While crossing a deep ravine the Spanish cavalry became disordered and Dagobert though he saw a chance to win a quick victory. He ordered the French right to attack the Spanish cavalry, and even moved troops from his left to support the attack.
The Duke d'Ossun saw this French movement, and took advantage of it to attack the French left wing. His cavalry folded up the remaining French infantry on the left, and reached the camp at Mas-d'Eu. The French right was also in trouble. Its advance had brought it into range of a battery of fourteen well placed Spanish guns, and was delayed for long enough to give the Spanish cavalry time to reform. The French infantry was forced to form squares, and Dagobert decided to order a retreat. Fortunately for him 1,200 new troops arrived from Perpignan in time to help support this retreat, and the French retreated back into the city.
This defeat caused panic in Perpignan. If Ricardós had advanced towards the city he may well have been able to capture it before a proper defence had been organised, but instead he decided to pull back to Le Boulou, on the Tech River, and capture the remaining French fortresses on the border. This delayed him by a month, and it was only after the fall of Bellegarde, on 25 June, that the Spanish made a serious effort to capture Perpignan.