In the War of the Austrian Succession he took part in the storming of Prague in 1742, and was made a brigadier. In 1744 and 1745 he saw further service on the Rhine, and he succeeded his father as duc de Broglie on the old duke's death in 1745. He was made a maréchal de camp, and he subsequently served with Marshal de Saxe in the Low Countries, and was present at Roucoux, Val and Maastricht. At the end of the war he was made a lieutenant-general.
During the Seven Years' War he served successively under d'Estrées, Soubise, and Contades, being present at all the battles from Hastenbeck onwards. His victory over Prince Ferdinand at Bergen (1759) won him the rank of marshal of France from the French King Louis XV and the title of Reichsfürst (prince of the Empire) from Emperor Francis I.
In 1760 he won an action at the Korbach, but was defeated at Villinghausen in 1761. After the war he fell into disgrace and was not recalled to active employment until 1778, when he was given command of the troops designed to operate against England. He played a prominent part in the French Revolution, which he opposed with determination; he commanded troops at Versailles in July 1789 and briefly served as Louis XVI's minister of war before fleeing France. After his emigration, the duc de Broglie commanded the "army of the princes" for a short time (1792). He died at Münster in 1804.