He became maréchal de camp in 1791, and, through the influence of Madame de Staël, was appointed Minister of War of Louis XVI. In this office he tried at all cost to impose his constitutional project, helped by the Bishop of Autun, Baumetz and Chapelier. But he showed incapacity in this post, and gave in his resignation. Despite his efforts, he did not carry his point, for in March 1792 the King, moved by intrigues and by the intransigence of those who surrounded him, thought right to dismiss him from that Ministry. His resignation was the result of his disagreements with the Feuillants on the question of foreign war. Narbonne-Lara and his friends hoped to bring on the war with Austria, by which they hoped to restore the prestige of the monarchy. Narbonne-Lara made an alliance with the Marquis de Lafayette, but their schemes were defeated. After his resignation, he joined the Army of the North and, in May 1792, he was elevated to Lieutenant General of the Army. After less than six months from his dismissal, the French Monarchy was agonizing, the French Republic was proclaimed and the Royal Family was incarcerated. Later, Narbonne actually incurred suspicion as a Feuillant. The comte de Narbonne-Lara also had on him a prison warrant. Due to this, and also to questions about his policy at the war office, he managed to seek refuge at the Embassy of Sweden, emigrated after 10 August 1792, and later evaded to London and from there to Germany, having visited England, Switzerland and Germany. During the Consulate, his friends Talleyrand and Fouché managed to remove his name from the list of the wanted, and returned to France in 1801, where he was retired with the patent of Divisional General.