Incipient brain-disease compelled him to withdraw from official life in November 1863, and he died at Spandau on the 26th of August 1865.
Meanwhile Bennigsen had prepared for a fresh undertaking, and leaving Lestocq with 20,000 Prussians and Russians to contain Bernadotte, who lay between Braunsberg and Spandau on the Passarge, he moved southwards on the 2nd, and on the 3rd and 4th of June he fell upon Ney, driving him back towards Guttstadt, whilst with the bulk of his force he moved towards Heilsberg, where he threw up an entrenched position.
In the interior only Spandau, Custrin, Magdeburg, Ingolstadt and Ulm were maintained as defensive supporting points, and similarly on the Rhine, which was formerly studded with fortresses from Basel to Emmerich, the defences were limited to New Breisach, Germersheim, Mainz, Cohlenz, Cologne and Wesel, all of a barrier character and not organized specially as centres of activity for field armies.
In 1850 he returned secretly to Germany, rescued Kinkel from the prison at Spandau and helped him to escape to Scotland.
In 1631, however, Gustavus Adolphus marched on Berlin, compelled the elector to cede the fortress of Spandau, and to aid him with men and money.