[2] He then served as first officer on the cutter Lézard, under his older brother Tromelin-Launay, departing Lorient in October 1772 to arrive at Isle de France (Mauritius) in June 1773.
On the way, he repelled an attack from a British privateer, which earned him the Cross of the Order of Saint Louis and a promotion to Lieutenant.
[2] During the War of American Independence, Tromelin-Lanuguy served in the Indian Ocean in a squadron under Rear-Admiral Thomas d'Estienne d'Orves.
[5][2] In March 1782, in the wake of the Battle of Sadras, Suffren transferred Tromelin-Lanuguy to Pourvoyeuse, replacing Lieutenant de Ruyter.
[2] In April 1782, Tromelin-Lanuguy escorted prizes captured by Bellone to Tharangambadi,[2] and from there sailed to Malaca to procure supplies and spare parts.
[2] Upon his return, Tromelin-Lanuguy suffered the scorn of Suffren, who blamed him for failing to press his attack on the East Indiamen.
He then requested permission to leave for Isle de France, but actually emigrated to join the Armée des Princes.