Following the death of Charles VII, Seckendorff negotiated a reconciliation between Austria and Bavaria in the Treaty of Füssen on 22 April 1745. Emperor Francis I reaffirmed all of Seckendorff's honors, and the diplomat retired to his estate at Meuselwitz in Thuringia. In 1757 the death of his wife, for whom, harsh and unamiable as he was, he had a deep and abiding affection, broke down his already failing health. Frederick the Great directed Prussian hussars to abduct Seckendorff from Meuselwitz in December 1758 during the Seven Years' War. After spending half a year in detention in Magdeburg, he was exchanged for Moritz of Anhalt-Dessau, who had been captured by Austrians at Hochkirch. Returning to Meuselwitz, Seckendorff died at his estate in 1763.