In 1803, as adjutant to General von Rüchel and motivated by him, Knesebeck wrote a memorandum to the Duke of Brunswick as to the effect of the need of a Landwehr (militia), which he called "the Legion of Honour" of the Prussian state.
For most of the War of the Fourth Coalition in 1806, Knesebeck served with General Rüchel's staff.