MONTALEMBERT, MARC RENE, MARQUIS DE (1714– 1800), French military engineer and writer, was born at Angou lerne on July 16, 1714, and entered the French army in 1732. He fought in the War of the Polish Succession on the Rhine (1733– 34), and in the War of the Austrian Succession made the cam paigns of 1742 in Bohemia and Italy. In the years preceding the Seven Years' War, Montalembert devoted his energies to the art of fortification, to which Vauban's Traite de l'attaque attracted him, and founded the arsenal at Ruelle, near his birthplace. On the outbreak of war he became French commissioner with the allied army of Sweden, with the rank of brigadier-general. He constructed the field fortifications of Anklam and Stralsund. In 1761 he was promoted marechal de camp, and began the works on which his fame rests. Montalembert's fortress has been aptly described by an English author as an "immense battery." The intricacies of trace by which Vauban and Cormontaigne sought to minimize the power of the attack are abandoned in favour of a simple tenaille plan so arranged that the defenders can bring an overwhelming fire to bear on the works of the besieger.
Montalembert, who himself drew his idea from the practice of Swedish and Prussian engineers, furnished the German construc tors of the early 19th century with the means of designing en trenched camps suitable to modern conditions of warfare. The "polygonal" method of fortification is the direct outcome of Montalembert's systems. In his own country the caste-spirit of
the engineer corps was roused to defend Vauban, and though Montalembert was allowed to construct some successful works at Aix and Oleron, he was forbidden to publish his method, and given but little opportunity for actual building. After fifteen years of secrecy he published in Paris (1776-1778) the first edition of La Fortification perpendiculaire. At the time of the Revolution he emigrated for a time. After his return Carnot often called him into consultation on military affairs, and, in 2792, promoted him general of division. He died in Paris on March 29, 180o. His wife, Marie Josephine de Comarieu, was the hostess of one of the best-known salons of Louis XVI.'s time. He withdrew his candidature to the Institut in favour of General Buonaparte.
Besides his masterpiece, he wrote L'Art defensive superieure a l'offensif (1793 ; in reply to attacks made upon his earliest work, La Fortification perpendiculaire, of which in later editions it forms part) ; Memoire historique sur le fonte des canons (Paris, 1758), and other works on the same subject; Correspondance pendant la guerre de 1757-1760 (London, 1777) ; Rotation des boulets (Acad., 1755) ; and Relations du siege de S. Jean d'Acre (Paris, 1789). See Tripier, La Fortification deduite de son histoire (Paris, 1866).