Lhermite started sailing at the age of eight in the merchant navy, steadily rising in rank until he was promoted to captain in 1787.
[3] In the following years, Lhermite undertook missions in Dunkirk, Rotterdam and Vlissingen, and organise the commissioning of a naval division in the Netherlands, bound for Santo Domingo to ferry troops.
[3][4] In Santo Domingo, he took command of the 74-gun Duguay-Trouin, on which he recaptured Petit-Goâve from the Haitian Revolutionaries, destroying her harbour and the village of Arcahaie afterwards.
[5] Lhermite, his armament diminished and fearing a ruse to lure him into a trap, decided against chasing the British ship.
[3] In Missiessy's absence, he replaced him and acted as préfet maritime and overall commander of the French naval forces in the North Sea.