After the Peace of Schönbrunn Willisen took vacation from the Austrian Army but did not return into service. He lived in Teutschenthal near Halle (Saale), where he was captured as a deserter in 1811 and imprisoned at Kassel. He escaped out of prison and returned into Prussian service after his official release out of Austrian service. Willisen fought in the &lt;a href="War%20of%20the%20Sixth%20Coalition%23War%20in%20Germany"&gt;Napoleonic battles of 1813/14&lt;/a&gt; as a member of the staff of the Prussian “Silesian Army” and became a captain in Gebhard Leberecht von Blücher’s staff in 1815. He remained in the Prussian generalstaff after Napoleon’s defeat and became a teacher of “Art of War” and “History of War” at the Prussian Military Academy. He published several books and opposed the views of Carl von Clausewitz. About 1830 Willisen also criticized the Russian warfare in the Napoleonic wars and showed his sympathy towards the Polish Uprisings in Congress Poland and the democratic movement in general.