He was born at Foix and educated at the École Polytechnique. He entered the government service as a mining engineer (see X-Mines). In 1858 he was appointed traffic manager to the Compagnie de chemins de fer du Midi, a post in which he showed a remarkable talent for organization, and in 1862 returned to the engineering service, attaining in 1886 the rank of inspector-general. He was sent on several special scientific missions, including one to the UK, on which he wrote a notable Mémoire sur le travail des femmes et des enfants dans les manufactures de l'Angleterre (1867).
On the establishment of the Third Republic in September 1870, he offered his services to Léon Gambetta, was appointed prefect of the department of Tarn-et-Garronne, and in October became chief of the military cabinet. It was mainly his powers of organization that enabled Gambetta to raise army after army to oppose the invading Germans. He showed himself a strategist of no mean order; but the policy of dictating operations to the generals in the field was not attended with happy results. The friction between him and General d'Aurelle de Paladines resulted in the loss of the advantage temporarily gained at Orleans, and he was responsible for the campaign in the east, which ended in the destruction of Bourbaki's army.
In 1871 he published a defence of his administration under the title of La Guerre en province pendant le siege de Paris. He entered the Senate in 1876 as a follower of Gambetta, and in December 1877 became minister of public works in the Dufaure cabinet. He carried a great scheme for the gradual acquisition of the railways by the state and the construction of new lines at a cost of three milliards, and for the development of the canal system at a further cost of one milliard. He retained his post in the ministry of Waddington, whom he succeeded in December 1879 as president of the council and minister for foreign affairs. He passed an amnesty for the Communists, but in attempting to steer a middle course on the question of the religious associations, lost Gambetta's support, and resigned in September 1880.
In January 1882 he again became president of the council and minister for foreign affairs. His refusal to join England in the bombardment of Alexandria was the death-knell of French influence in Egypt. He attempted to compromise by occupying the Isthmus of Suez, but the vote of credit was rejected in the Chamber by 417 votes to 75, and the ministry resigned. He returned to office in April 1885 as foreign minister in Henri Brisson's cabinet, and retained that post when, in January 1886, he succeeded to the premiership.
He came to power with an ambitious programme of internal reform; but apart from settling the question of the exiled pretenders, his successes were chiefly in the sphere of colonial extension. In spite of his unrivalled skill as a parliamentary tactician, he failed to keep his party together, and was defeated on December 3 1886. In the following year, after two unsuccessful attempts to construct new ministries, he stood for the presidency of the republic; but the radicals, to whom his opportunism was distasteful, turned the scale against him by transferring the votes to Sadi Carnot.
In April 1888 he became minister of war in Charles Floquet's cabinet--the first civilian since 1848 to hold that office. His services to France in this capacity were the crowning achievement of his life, and he enjoyed the conspicuous honour of holding his office without a break for five years through as many successive administrations--those of Floquet and Pierre Tirard, his own fourth ministry (March 1890-February 1892), and the Loubet and Ribot ministries. To him were due the introduction of the three-years' service and the establishment of a general staff, a supreme council of war, and the army commands. His premiership was marked by heated debates on the clerical question, and it was a hostile vote on his Bill against the religious associations that caused the fall of his cabinet. He failed to clear himself entirely of complicity in the Panama scandals, and in January 1893 resigned the ministry of war.
In November 1898 he once more became minister of war in the Dupuy cabinet, but resigned office on May 61899.