Three years later Rüstow accompanied Giuseppe Garibaldi in the famous expedition against the Two Sicilies as colonel and Chief of staff, and to him must be ascribed the victories of Capua (10 September 1860) and Volturno (1 October 1860). At the end of the campaign he settled down in Zürich. At the outbreak of the 1870 Franco-Prussian War, he offered his services to Prussia, but was rejected. In 1878, on the foundation of a military professorship at Zürich, Rüstow applied for the post, but taught only short, and, on its being given finally to another officer (Emil Rothpletz), lost heart and committed suicide at Aussersihl near Zürich.