27 August 1798: The Battle of Castlebar on this day. General Humbert of the French Revolutionary Army defeated the forces of the British Army under General Lake. Five days previously Humbert had landed in Killala Bay with a small force that the Directory in Paris had dispatched to help the Irish overthrow British rule in Ireland. While other expeditions had been launched his was the only one to make it ashore. He had with him some 1,000 men & 3 cannons but large supplies of armaments to equip many more. 

After advancing and taking the town of Ballina he turned south to take Castlebar. It was here that General Lake, who had ruthlessly crushed the Wexford Rising some months earlier decided to make a stand. He had a formidable force at his disposal comprising of around 2/3,000 men and about 10 cannon. He had his men deploy in the direction he expected the Franco- Irish army to advance from. It seems that word leaked out about this and Irish sympathisers informed the French general of the British dispositions. He was advised to take a route around the western edge of Lough Con and approach his objective from an unexpected angle thus hoping to catch his enemy off guard.

 In this he was successful and when he was sighted on the outskirts of the town the British had to hastily re-deploy their forces to block him from taking them in the flank. They managed to achieve this but they had been rattled and that played right into Humbert's hands.

Humbert decided to launch a head on attack as time was the essence to stop the defenders regaining their composure and he gave the order for his men to take the position by storm. While the British force was bigger [perhaps 2,500] it was mostly militiamen and fencibles while the French had some 800 regular soldiers along with about 1,000 Irish volunteers.

...then at 7 am in the morning of 27 august, Humbert found himself faced with formidable opposition: a front line manned by the Kilkenny Militia, commanded by the marquis of Ormond, and the Royal Irish Artillery with four curricle guns; a second line of Fraser Fencibles from the highlands with two cannon, and a corps of Galway yeoman; a third line consisting of four companies of Longford militia commanded by Lord Granard; and, in reserve, squadrons of carabineers and Lord Roden’s Foxhunters.

A History of Ireland in 250 episodes 

Jonathan Bardon

 In the event the shock of the melee by the men of Le Armée Révolutionnaire Française broke the British lines and they fled through the streets of the town.  Locals soon dubbed their defeat ‘the races of Castlebar’ and were elated that such a humiliating defeat had been inflicted on such a ruthless officer as General Lake was known to be. To add further to his misery his personal baggage was captured and looted as he fled the battlefield. 

Although achieving a stunning victory, the losses of the French and Irish were high, losing about 150 men, mostly to the cannonade at the start of the battle and most of them experienced French Regulars. The British suffered over 350 casualties of which about 80 were killed, the rest either wounded or captured, including perhaps 150 who joined the republicans. However Humbert’s luck was not to hold and some days later he was cornered by General Cornwallis with an overwhelming force and he had to surrender.