After receiving a light sentence in his country of suspension for six months, Brunet rejoined the French army in February 1870, with only a slight loss in seniority. During the Franco-Prussian War of 1870–1871 he distinguished himself at the battles of Spicheren, Mars-la-Tour and Gravelotte. He was taken prisoner at the Siege of Metz. In the aftermath of the war Brunet played a key role as a member of the Versailles Army in the suppression of the Paris Commune. He visited the Royal School of Military Engineering in the United Kingdom in August 1871, and later that year was made an officer of the Légion d'honneur and assigned as aide de camp to the Minister of War, Ernest Courtot de Cissey.