Frederick II promoted Wedel to lieutenant general on 22 February 1759. In July, he was transferred command of the Dohna Corps, Frederick deciding the Christoph von Dohna was too ill to continue. Frederick sent Wedel to thwart the Russian advance into Brandenburg with 28,000 men; these were not enough. Due to Wedel's poor management and aggressiveness—he was ordered to attack a Russian army one-and-a-half times his size—they were crushed at the Battle of Kay. This loss left the road to Berlin open, and Frederick was forced to hurry north to Frankfurt an der Oder to repel the Russian and Austrian allied armies. At the subsequent Kunersdorf, Wedel was severely wounded. Health problems forced him to retire from active service in 1760.