In the army he was made Lieutenant General of the King's armies and had command over the Artois regiment from 1747 to 1762. Here he impressed the King and was promoted to Colonel within the same regiment.
Louis must have wanted to acquire a title for himself for he married Etienette Fizeau de Clérmont who brought him the title of Marquis de Moy. However, at court he would still be known as the Comte de Brienne. The couple had adopted the three sons of his cousin but had none of their own. Sadly, all of his sons were guillotined during the revolution.
Here he established a "little court" for himself and his friends where they would enjoy theatres, hunting parties and discussions on philosophy. Louis also established quite an impressive collection of minerals and was often visited by natural scientists.
In 1787 he followed his brother's footsteps and became a secretary of state to Louis XVI - he remained in this position only for a year before he resigned. His appointment raised a few eyebrows but not because of his character. Instead, people wondered that he only joined the council after his brother -the Archbishop of Sens - had left it.
During the revolution the Loménie family was widely recognised as having embraced the new world order. Louis was rather popular and his success with the military only heightened that. However, Robespierre soon came to view his popularity as a threat and had him and his adopted sons arrested.
Louis was guillotined on 10 May 1794 alongside Madame Élisabeth, sister of Louis XVI.