Jean-François de Galaup embarked in March 1757 on the Célèbre in the squadron commanded by Count Dubois de La Motte and sent to the rescue of Louisbourg, on Île Royale. He escaped the terrible epidemic that ravaged the ships and the city of Brest where he returned on November 12, 1757.
On February 22, 1758, he embarked on the frigate La Zéphyr as part of the squadron sent to Louisbourg by Louis Charles du Chaffault, Count of Besné, to rescue Louisbourg again. On August, La Pérouse moved to Le Cerf and then, on May 16, 1759, to the vessel Le Formidable in the squadron that the Count of Conflans was painstakingly preparing in Brest to protect a possible landing in England.
On November 20, this squadron of twenty-one ships collided at the entrance to Quiberon Bay with twenty-three British ships commanded by Admiral Hawke15. The Formidable, in the rear guard, had to bear the full brunt of the enemy attack and put up a good fight; La Pérouse received two wounds and, taken prisoner, was almost immediately exchanged.
Shortly before 4:00 p.m., the Formidable, admiral of the blue squadron, which had voluntarily slowed down to support its ships, threatened to sink low in an action where the same cannonball killed the two brothers Saint-André du Verger: Louis had his head blown off and Marc-Antoine’s body was cut in two. Completely helpless, reduced to a “carcass covered with corpses” after having been hit by at least fifteen adversaries, he was forced to drop his flag as the rest of the English squadron arrived on the battlefield. The Formidable was moored by the Resolution. Among the survivors of the ship was the young Lapérouse, future explorer of the Pacific under Louis XVI.
In May 1762, La Pérouse embarked on the Robuste, in the division commanded by the Chevalier de Ternay, which went to destroy the British fisheries in Newfoundland. In September 1763, Bidé de Chézac took with him some Guardsmen of the Navy, including Lapérouse, to lead from Lorient to Brest the new ship Les Six Corps.