The young man was educated at the Ecole polytechnique and commissioned in the artillery in 1877.
His career before World War I was a varied one, combining regimental duties, staff assignments, and a long turn teaching at the War College. Fayolle fought in Tunisia in 1881 and advanced to captain in 1883. He completed the War College with distinction in 1891, held a series of staff positions in Paris, then returned to the War College in 1894 as assistant professor of artillery. He became the chief professor in the artillery course in 1897, a position that he held until 1908. His fellow instructors included Pétain, who taught tactics, and Foch who taught the infantry course. Following his term at the War College, Fayolle took a series of line commands. He led a regiment and then a brigade, the latter position ap-parently marking the close of his career: he retired in early 1914 after reaching the age limit for a brigadier general. A reserved and modest personality, a devout Catholic without spectacular colonial service on his record, Fayolle had found no chance for rapid advancement in the peacetime military.
In August 1914, Fayolle was recalled to active duty to assume command of the Seventieth Infantry Division, a force made up largely of reservists. His unit advanced as part of Foch's XX Corps toward Morhange, then took part in the subsequent retreat and bitter defensive battles east of Nancy in late August and early September. At the close of September Fayolle's men joined in the race to the sea and ended in a defensive position north of Arras. There Pétain became his corps commander. Much of Fayolle's wartime service was thereafter dominated by his role as Pétain's military workhorse and key subordinate.
The two former teachers at the War College agreed from the start of hostilities on the futility of ambitious infantry assaults unsupported by adequate artillery fire. Both pessimistically foresaw a long war dominated by defensive tools: the trench, the machine gun, and barbed wire. In June 1915, Fayolle was promoted; he succeeded Pétain as commander of the XXXIII Corps during the limited but costly success of the Artois offensive.
Fayolle increasingly criticized Foch and Joffre, the ranking commanders of the French army in 1915, for demanding such attacks without sufficient resources. As an artilleryman himself, Fayolle saw the necessity for superior strength in this arm of the service: the enemy's artillery had to be overwhelmed in order to permit limited and methodical advances by French troops. Like Pétain, he believed that successful attacks must be halted periodically so that the artillery could be brought up in force to prepare for the next step forward. In the existing military framework, ambitious hopes for a breakthrough were illusions.
Moreover, he hoped that economic pressure, or perhaps a breakthrough in the Balkans, would end the hopeless deadlock in France.
Fayolle was promoted to command the Sixth Army in February 1916, and he conducted limited advances between the Somme and the Aisne to relieve the pressure on Verdun. He led his army on the southern flank of the British Expeditionary Force (BEF) during the huge offensive on the Somme (July-September 1916). His advance far outstripped that of his British neighbors, whom he criticized for employing "infantile tactics." These months were also marked by growing friction with Foch, whom Fayolle reviled for "scratching out" meaningless gains at heavy cost in French lives. Marked down as too cautious and prudent, Fayolle was moved from command of the Sixth to the First Army in early 1917. Joffre's successor, General Nivelle, wanted his protégé, General Mangin, to spearhead the coming spring offensive with the Sixth Army. Following the debacle of April 1917, Fayolle again filled Pétain's shoes, taking command of the Center Army Group as Pétain rose to become commander in chief. Fayolle's forces attacked with success at Verdun in late August; this was the first of Pétain's cautious and limited offensive operations following the spring mutinies.
The Italian defeat at Caporetto in October 1917 led to Fayolle's departure over the Alps in mid-November. Foch was already on the scene, and the French troops in Italy repeatedly became a bone of contention between him and Pétain. Fayolle's Tenth Army in Italy, along with the British forces under General Plumer, held the mountain passes protecting the northern flank of the Piave line, and the shaken Italian army was able to pull itself together by the close of 1917.
Fayolle returned to France in March 1918 to take command of a multinational reserve army of forty divisions under Foch's direction. Fayolle was to hold the crucial sector of the western front stretching from the Oise northward to Péronne, that is, the hinge where the French and the British armies met. The final months of the war saw Fayolle tugged back and forth by Foch, the supreme Allied commander, and Pétain, the French commander in chief, as the Allies first struggled to parry a series of German offensives, then began to take the war to the enemy. In the final week of March, as Ludendorff threatened to seize Amiens and to push apart the French forces and the BEF, Foch called on Fayolle to hold Amiens at all cost; meanwhile, Pétain encouraged his old friend to keep open the option of retreating southward to cover Paris. Luckily, by March 27/28, the German offensive bogged down after opening a small gap between Fayolle and the British.
In May Foch ordered Fayolle to hold every foot of territory against new German onslaughts; Pétain countered with a demand for a defense in depth. To Fayolle, his old friend Pétain seemed to be shaken psychologically by this time; sometimes the French commander radiated optimism, but more often seemed plunged into a paralysis of pessimism. As the way opened for French counterattacks, Fayolle came to put aside old quarrels to accept as a virtue Foch's single-minded aggressiveness. In mid-July, for example, Fayolle prepared to counterattack the western edge of the enemy's Marne salient. Pétain intervened to call off the operation, and a delighted Fayolle received word on July 16 that Foch had overruled the French commander in chief.
By the close of September, Fayolle had fulfilled Foch's directive to the Allied armies to destroy all enemy salients in his sector, just as the BEF north of the Somme and General Maistre and his Central Army Group on Fayolle's right had done. Fayolle drove his troops steadily forward until the November armistice. He then led the Army of Occupation to its headquarters at Mainz on December 14. At the peak of the action during the final summer of the war, Fayolle had controlled fifty-five divisions, one-half the total fighting strength of the French army. But in October 1919, he quietly gave up his command of the occupation forces on the Rhine and, the year following, went into retirement.
A public clamor, stirred up by the press, brought Fayolle back into service. Still only a brigadier general on the official army records, Fayolle was promoted marshal of France in 1921. He went on special missions to Canada and Italy, then remained at least nominally on active duty as a member of the Supreme War Council until his death, August 27, 1928, in Paris.