Marmont was born at Châtillon-sur-Seine, the son of an ex-officer in the army who belonged to the petite noblesse and adopted the principles of the Revolution. His love of soldiering soon showed itself, and his father took him to Dijon to learn mathematics prior to entering the artillery, and there he made the acquaintance of Napoleon Bonaparte, which he renewed after obtaining his commission when he served in Toulon.
The acquaintance ripened into intimacy; Marmont became General Bonaparte's aide-de-camp, remained with him during his disgrace and accompanied him to Italy and Egypt, winning distinction and promotion to general of brigade. In 1799 he returned to Europe with his chief; he was present at the coup d'état of the 18th Brumaire, and organized the artillery for the expedition to Italy, which he commanded with great effect at Marengo. For this he was at once made general of division. In 1801 he became inspector-general of artillery, and in 1804 grand officer of the Legion of Honour, but was greatly disappointed at being omitted from the list of officers who were made marshals.
In 1805 he received the command of a corps, with which he did good service at Ulm. He was then directed to take possession of Dalmatia with his army, and occupied the Republic of Ragusa. For the next five years he was military and civil governor of Dalmatia, and traces of his beneficent régime still survive both in great public works and in the memories of the people. In 1808 he was made duke of Ragusa.
In the War of the Fifth Coalition, he defeated an Austrian holding force in the Dalmatian Campaign of May 1809 and captured the opposing commander. Breaking out of Dalmatia, he reached Ljubljana (Laibach) in early June. After he defeated Ignaz Gyulai's corps in the Battle of Graz, Napoleon summoned the XI Corps to Vienna. He arrived in time to fight in the Battle of Wagram on 5 and 6 July. In the subsequent pursuit of Archduke Charles, Marmont got his corps into a difficult spot and was rescued only by the arrival of Napoleon with heavy reinforcements. Napoleon made him a Marshal of France, though he said, "Between ourselves, you have not done enough to justify entirely my choice." Of the three marshals created after Wagram, the French soldiers said,
MacDonald is France's choice
Oudinot is the army's choice
Marmont is friendship's choice.
He was appointed governor-general of all the Illyrian provinces of the empire. In July 1810 Marmont was hastily summoned to succeed Masséna in the command of the French army in the north of Spain. His relief of Ciudad Rodrigo in the autumn of 1811 in spite of the presence of the British army was a great feat, and in the manoeuvring which preceded the battle of Salamanca he had the best of it. But Wellington more than retrieved his position in the battle, and inflicted a severe defeat on the French. Marmont and his deputy commander Comte Jean-Pierre François Bonet were both struck by shrapnel very early in the battle. Marmont was gravely wounded in the right arm and side and command of the battle passed to Bertrand Clausel. He retired to France to recover.
In April 1813 Napoleon gave him the command of a corps, which he led at the battles of Lützen, Bautzen and Dresden. He then fought throughout the great defensive campaign of 1814 until the last battle before Paris. Marmont's forces fought a fighting retreat back to the commanding position of Essonne, inflicting high casualties on the enemy.
Marmont then took upon himself a political role, seeking to halt what he now saw as a pointless prolonging of a war which France would now assuredly lose. Marmont contacted the Allies and reached a secret agreement with them. As the Allies closed on Montmartre, Marmont—together with marshals Mortier and Moncey—marched to a position where they were quickly surrounded by Allied troops and then surrendered their forces, as had been agreed.
Marmont stayed loyal to the restored Bourbon king Louis XVIII during the Hundred Days, and following Waterloo voted in favour of the execution of Marshal Ney.
He was made a peer of France and a major-general of the royal guard, and in 1820 a knight of the Order of the Holy Spirit and a grand officer of the Order of St Louis. He was the major-general of the guard on duty in July 1830 during the July Revolution, and was ordered to put down with a strong hand any opposition to the ordinances. Himself opposed to the court policy, he yet tried to do his duty, and only gave up the attempt to suppress the revolution when it became clear that his troops were outmatched. This brought more obloquy upon him, and the Duke d'Angoulême even ordered him under arrest, saying:
Will you betray us, as you betrayed him?
Marmont accompanied the king into exile and forfeited his marshalate. His desire to return to France was never gratified and he wandered in central and eastern Europe, settling finally in Vienna, where he was well received by the Austrian government, and, strange to say, made tutor to the duke of Reichstadt, the young man who had once for a few weeks been styled Napoleon II. Despite his long friendship with Napoleon, by this time the verb "raguser"—derived from his title, the Duke of Ragusa—was a household word in France: it meant "to betray". He died at Venice in March 1852, the last living Napoleonic Marshal.
In his last years, Marmont spent much of his time working on his Mémoires, which are of great value for the military history of the time.
His works are:Voyage en Hongrie, etc. (4 vols., 1837)
Voyage en Sicile (1838); trans. it., Milan, 1840
Esprit des institutions militaires (1845)
Cesar; Xenophon; and Mémoires (8 vols., published after his death in 1856)
In 1798 Marmont married Hortense de Perregaux, the daughter of Jean-Frédéric Perregaux, a Swiss (and Protestant) banker, later a founder and regent of the Banque de France, and Adélaïde de Praël de Surville, herself the natural daughter of the banker to the court of Louis XV, Nicolas Beaujon. They had no children and were divorced in 1817. She outlived him by five years, dying in Paris in 1857.
Marmont is perhaps one of the most controversial marshals created under the Empire. His reputation was tarnished by the betrayal of Napoleon and his defeat at Salamanca. However, on the whole Marmont's military career was quite impressive. He was perhaps the most educated of the marshals and one of the few to write a thesis on the art of war. He was a talented strategist, understanding the art of command and the movement of troops. He performed wonderfully in Dalmatia making what John Elting calls "a remarkable 300 mile march through frequently roadless country, scattering two Austrian forces, but clinging to his independent status..." Perhaps even more impressive is his study and evaluation of the Spanish theater of the war. He studied Wellington's nature of war, refusing to give battle against the English unless the ground was of Marmont's choosing. This led to a series of maneuvers where Marmont frequently had the upper hand. Marmont understood the importance of cooperation in the Peninsula by supporting his fellow marshals. Tactically Marmont was deadly and quick to strike, but prone to sloppiness which caused him his two defeats.