In 1672, having finished his philosophy course, he was given a scholarship at the college of St Michel at Paris by Jean, marquis de Pompadour, lieutenant-general of the Limousin.
In the campaign of 1744-48 and attained high military rank, which he owed more to his courtiership than to his generalship. Soon after the beginning of the Seven Years' War, through the influence of Mme de Pompadour, he was put in command of a corps of 24,000 men, and in November 1757 he sustained the crushing defeat of Rossbach.
Though she denied that she had ever written directly to Madame de Pompadour, it is certain that she allowed her ministers to make use of the favourite's influence over the French king.
He was much employed, owing to Richelieu's influence, in the fetes of the dauphin's marriage, and was rewarded through the influence of Madame de Pompadour on New Year's Day 1745 by the appointment to the post of historiographer-royal, once jointly held by Racine and Boileau.
He engaged in a foolish and undignified struggle with Crebillon (not fils), a rival set up against him by Madame de Pompadour, but a dramatist who, in part of one play, Rhadamiste et Zenobie, has struck a note of tragedy in the grand Cornelian strain, which Voltaire could never hope to echo.
In France, Madame de Pompadour was their enemy because they had refused her absolution while she remained the king's mistress; but the immediate cause of their ruin was the bankruptcy of Father Lavalette, the Jesuit superior in Martinique, a daring speculator, who failed, after trading for some years, for 2,400,000 francs and brought ruin upon some French commercial houses of note.
It appears certain that they were brought to France, only much later, as a present to Mme de Pompadour, although the de Goncourts, the historians of the mistresses of Louis XV., have failed to trace any records of this event.
Although Conti did not secure the Polish throne he remained in the confidence of Louis until 1755, when his influence was destroyed by the intrigues of Madame de Pompadour; so that when the Seven Years' War broke out in 1756 he was refused the command of the army of the Rhine, and began the opposition to the administration which caused Louis to refer to him as "my cousin the advocate."
The intrigues of Madame de Pompadour played in this change an important though not a decisive part.