First commands and governor-general of Saint-Dominique
He was made lieutenant in 1727 and carried out two campaigns in the Mediterranean. Then, in 1731, he served as lieutenant of the gardes de la Marine at Rochefort. The following year he was made knight of the Order of Saint Louis and from 1733 to 1734 commanded a flotilla charged with guarding the transport of men and munitions to Cayenne and Martinique. That same year, he was promoted to captain, and served again under Duguay Trouin then under the marquis d'Antin during the War of the Polish Succession. In 1741, he commanded the gardes de la Marine school at Brest, where he had begun his career. Eventually, he was put in command of the Content and captured the British ship of the lineNorthumberland on 8 May 1744. On board the Terrible he escorted Atlantic convoys. In 1747, he was made governor-general of Saint-Domingue, but on the voyage to take up the post his vessel was engaged by British warships and his ship was captured. He was freed in 1748, thanks to the treaty of Aix la Chapelle, on which he was made "chef d'escadre", a role he held up to 1751. In 1752 he became lieutenant général of the navy.
In 1759, he was put in charge with landing troops in Scotland for an invasion of England organised by Louis XV, Nicolas René Berryer and the marshal of Belle-Isle, and named "le Grand Dessein de débarquement". Command of the expeditionary force was given to Emmanuel-Armand de Richelieu, duc d'Aiguillon. Relations between Conflans and Aiguillon were far from cordial and, in effect, Conflans disagreed with the conduct of the campaign by his superiors and informed the king that he was anxious to avoid battle with the British fleet under Edward Hawke. The fleet was mustered in the gulf of Morbihan, and it was there that Conflans had to start his escort duties. Finally, Hawke momentarily relaxed his blockade of Brest in order to avoid a storm and Conflans got out of Brest on 14 November. Opposing currents diverted the marshal from his initial route and Conflans did not sight Belle Île until the 20th. Meanwhile, Hawke had been warned of Conflans's departure and moved to block his path. On 20 November on a stormy sea, Conflans sighted Duff's squadron retreating and gave the order to attack it, but shortly thereafter Hawke's fleet sighted Conflans's. Duff then put about so that Conflans turn aside to chase him, thus allowing Hawke to bring his fleet into line of battle and begin pursuing the French fleet. Conflans decided to sail into Quiberon Bay, and engage Hawke there, even though Hawke had caught up with Conflans just as the French fleet began to enter the bay. Hawke nevertheless joined battle and decisively crushed the French fleet, capturing one, destroying three and sinking two. Conflans moved to the safety of a ship in his rear, but night soon put a temporary end to the battle. During the night, Conflans's flagship, the Soleil Royalran aground, without his knowing, within only a few cable lengths of the British fleet. When dawn rose, he realized the danger that awaited him and sailed across the Croisic to embark on the French vessel Héros. He then burned his flagship after evacuating it. On his return to Brest, Conflans would not only have to explain his defeat but also his burning of his flagship. His choice to engage in the bay of Quiberon was criticized, because it reckoned without the audacity of Hawke. The reasons for his decision to abandon his vessel remain obscure. He was reproached for it at the time. Disgraced, he passed his last years in Paris where he died in 1777. His post of vice admiral of the Ponant would be given to the Joseph de Bauffremont, his subaltern at Quiberon Bay.
