Witzleben achieved the rank of Second Lieutenant in 1802. He was captured in the Battle of Jena–Auerstedt fought on 14 October 1806, but was exchanged in August 1807. His work "Ideas on the Reorganisation of the Light Infantry", caught the attention of Gerhard von Scharnhorst, so that he was transferred in December 1808 to the newly formed "Garde-Jäger-Bataillon" as a Stabskapitän. In early 1812 he was promoted to major and fought on 2 May 1813 in the Battle of Lützen. During the war in France he was promoted to lieutenant colonel. In spring 1815 he joined the general staff of the army of Field Marshal Gebhard Leberecht von Blücher and was then made a colonel.