For 21 years Boyen lived in retirement, occupying himself with historical studies, until King Frederick William IV, immediately after ascending the throne, recalled him to active service, and promoted him to general of the infantry. In March 1841 he once again took over the War Ministry, though without achieving a great influence in the general political situation. He resigned in November 1847, received the rank of field marshal, and died on 15 February 1848. The King named the fortress of Lötzen in East Prussia after him.