Bronsart participated in the Austro-Prussian War of 1866 as a member of the II Corps general staff, and fought in the Battle of Gitschin and Königgrätz. During the Franco-Prussian War of 1870/71 he was chief of a section on the Great General Staff headquarters, and conducted the preliminary negotiations for the surrender of the French at the Sedan fortress. After the war Bronsart was made "Oberst" (colonel) and Chief of Staff of the Guard Corps, becoming major general in 1876, commander of the 1st Guards Infantry Brigade in 1878, and lieutenant general (with a 2nd Guards Infantry Division command) in 1881.