In December 1796, during the French Revolutionary Wars, a French expeditionary force departed from Brest on an expedition to invade Ireland. This army of 18,000 French soldiers was intended to link up with the secret organisation of Irish Republicanism known as the United Irishmen and provoke a widespread uprising throughout the island. It was hoped that the resulting war would force Britain to make peace with the French Republic or risk losing control of Ireland altogether. Led by Vice-Admiral Morard de Galles, General Lazare Hoche and leader of the United Irishmen Wolfe Tone, the invasion fleet included 17 ships of the line, 27 smaller warships and transports, and carried extensive field artillery, cavalry and military stores to equip the Irish irregular forces they hoped to raise.
Departure from Brest
Morard de Galles planned to sail his fleet from the French naval fortress of Brest under cover of darkness on the night of 15–16 December. The British Channel Fleet normally maintained a squadron off Brest to blockade the port, but its commander, Rear-Admiral John Colpoys, had withdrawn his force from its usual station 20 nautical miles (37 km) offshore to 40 nautical miles (74 km) northwest of Brest because of severe Atlantic winter gales. The only British ships within sight of Brest were an inshore squadron of frigates under Sir Edward Pellew in HMS Indefatigable, accompanied by HMS Amazon, HMS Phoebe, HMS Révolutionnaire and the lugger HMS Duke of York. Pellew was already renowned, having been the first British officer of the war to capture a French frigate: the Cléopâtre at the Action of 18 June 1793. He later captured the frigates Pomone and Virginie in 1794 and 1796, and saved 500 lives following the shipwreck of the East Indiaman Dutton in January 1796. For these actions he had first been knighted and then raised to a baronetcy. Indefatigable was a razee, one of the largest frigates in the Royal Navy, originally constructed as a 64-gun third rate and cut down to 44 guns in 1795 to make the ship fast and powerful enough to catch and fight the largest of French frigates. Armed with 24-pounder cannon on the main decks and 42-pounder carronades on the quarter deck, she had a stronger armament than any equivalent French frigate.
Observing the French fleet's departure from the harbour at dusk, Pellew immediately dispatched Phoebe to Colpoys and Amazon to the main fleet at Portsmouth with warnings, before approaching the entrance to Brest in Indefatigable with the intention of disrupting French movements. Believing that the frigates in the bay must be the forerunners of a larger British force, de Galles attempted to pass his fleet through the Raz de Sein. This channel was a narrow, rocky and dangerous passage, and de Galles used corvettes as temporary light ships that shone blue lights and fired fireworks to direct his main fleet through the passage. Pellew observed this, and sailed Indefatigable right through the French fleet, launching rockets and shining lights seemingly at random. This succeeded in confusing the French officers, causing the Séduisant to strike the Grand Stevenent rock and sink with the loss of over 680 men from a complement of 1,300. Séduisant's distress flares added to the confusion and delayed the fleet's passage until dawn. His task of observing the enemy completed, Pellew took his remaining squadron to Falmouth, sent a report to the Admiralty by semaphore telegraph, and refitted his ships.
Failure of the Expédition d'Irlande
During December 1796 and early January 1797, the French army repeatedly attempted to land in Ireland. Early in the voyage, the frigate Fraternité carrying de Galles and Hoche, was separated from the fleet and missed the rendezvous at Mizen Head. Admiral Bouvet and General Grouchy decided to attempt the landing at Bantry Bay without their commanders, but severe weather made any landing impossible. For more than a week the fleet waited for a break in the storm, until Bouvet abandoned the invasion on 29 December and, after a brief and unsuccessful effort to land at the mouth of the River Shannon, ordered his scattered ships to return to Brest. During the operation and subsequent retreat a further 11 ships were wrecked or captured, with the loss of thousands of soldiers and sailors.
By 13 January most of the survivors of the fleet had limped back to France in a state of disrepair. One ship of the line that remained at sea, the 74-gun Droits de l'Homme, was commanded by Commodore Jean-Baptiste Raymond de Lacrosse and carried over 1,300 men, 700–800 of them soldiers, including General Jean Humbert. Detached from the main body of the fleet during the retreat from Bantry Bay, Lacrosse made his way to the mouth of the Shannon alone. Recognising that the weather was still too violent for a landing to be made, Lacrosse acknowledged the failure of the operation and ordered the ship to return to France, capturing the British privateer Cumberland en route.