Along with many other officers who refused to serve under French command, Knesebeck sought his discharge from military service and returned to his estates in Neuruppin and Tylsen. In 1810 he was offered the role of military governor to the crown prince, but declined. During the War of the Fifth Coalition, in which Prussia did not participate, he received a secret order to observe enemy action in Austria and to report any opportunity for Prussia to enter the conflict. As such he attended the Battle of Aspern-Essling, which he viewed as a wasted victory. Though believing a Prussian intervention to be opportune, an accident prevented him from presenting his report to the king in person. His friend Heinrich von Kleist, now a civilian, had left a loaded pistol on the table in an inn near Aspern, which was fired by Knesebeck's adjutant in jest, hitting Knesebeck in the shoulder. The slowed correspondence with the king via messengers over the next weeks meant that by the time Knesebeck was ordered to offer the Austrians full support, the war was essentially lost.