Vaillant commanded the fortress at Algiers from 1837 to 1838, recalled to France, he was made director of the École polytechnique. Promoted to lieutenant general, Vaillant was put in charge of the building of the Parisian fortifications in 1845 under the command of Dode de la Brunerie. In 1849, Vaillant was given command of the engineers in the French expeditionary corps to Rome. Promoted to Marshal of France in 1851, Vaillant served as Minister of War from 1854 to 1859, holding the position throughout the Crimean War. On the outbreak of the Franco-Austrian War he resigned as Minister of War in order to serve as Chief of Staff to Napoleon III, who took personal command of the French Army. In 1860, Vaillant became minister responsible for the Imperial House and in 1864, he was made Grand Chancellor of the Legion d'Honneur. After the fall of the Second French Empire in September 1870, Vaillant was banished from France but was allowed back, returning in 1871. He died in Paris the next year.