French general, third son of the Marquis Michel de Curières de Castelnau; born at Rouergue on Christmas Eve 1851. He was educated first at the Jesuit college there, and later in Paris, and entered St. Cyr in 1869. When war broke out with Prussia the young cadet was posted to an infantry regiment, and he rose to the rank of temporary captain, being given a permanent commission as lieutenant when peace was made. He was promoted captain in 1876 and commandant in 1889. By 1893 his genius for organization had become apparent, and he was called to Paris by Gen. de Miribel. He remained at the Ministry of War for some six or seven years, during which time he perfected the French system of mobilization. That system remained in 1914 fundamentally the same as it had been conceived by him in 1900. On leaving Paris de Castelnau was promoted colonel. He was later given command of a brigade, and, in 1910, of a division. When Gen. Michel left the post of generalissimo and Joffre was appointed in his stead, Castelnau was designated as his chief-of-staff in case of war. But his religious and political views—he was nicknamed le capucin botté—caused him to be regarded with suspicion, and in consequence he was designated for the command, in case of war, of the II. Army in Lorraine, which command, on the outbreak of hostilities in 1914, he assumed. With Gen. Dubail (I. Army) he was responsible for the operations of August and September 1914 in Lorraine. The first offensive towards the Saar was unsuccessful, but his repulse of Prince Rupprecht’s VI. Army on the heights of the Grand Couronné, in August and September 1914, not only saved Nancy but paved the way for the Marne victory. He was made grand officer of the Legion of Honour. In the beginning of the “Race to the Sea” (Sept.–Oct.) the II. Army staff and its leader took command of the forces that were pushed into the region between the Oise and the Somme, and fought a series of encounter battles which ended in the stabilization of the front. In 1915 he took command of the group of four armies which constituted the French Centre, and he was in charge of the French offensive in Champagne in the latter months of the same year. On December 10, 1915, he was appointed “major-general of all the armies,” with the intention that he should be ad latus, and eventual successor of Joffre. But in practice, and partly as the result of political intrigue against him, Castelnau’s rôle was reduced to that of occasionally representing the commander-in-chief. It was in this capacity that he went to Salonika in the winter of 1915–16 to inspect the condition of affairs there, and it was in this capacity also that he performed his greatest service to France when, summoned at a moment’s notice to Verdun, he found the defence overpowered and disorganized by the suddenness of the German attack. The splendid part he played in steadying and inspiring the historic French resistance cannot easily be exaggerated. After a few days’ work he was able to hand over the defence, systematized, re-enforced and confident, to Pétain. In January 1917 after the appointment of Nivelle, many years his junior, to the chief command, he was sent on a mission to Russia. Returning in March of the same year he was given command of the eastern group of armies, and in this appointment he remained till the end of the war. In September 1917 he was awarded the médaille militaire. Political animosities alone prevented his being promoted to the dignity of Marshal of France, along with d’Espérey, Lyautey and Fayolle, in 1921.
