Participating in the wars against Napoleon, Leopold became imbued with a conservative, romantic spirit that was to remain part of him. He counted the patriotic poets Achim von Arnim and Heinrich von Kleist among his friends as well as the Prussian crown prince, who later became Frederick William IV. Always strongly religious, Leopold practiced a pietism then popular in Germany. Politically, he followed the conservative position of the Swiss political scientist Karl Ludwig von Haller and the German philosopher and politician F.J. Stahl, which advocated the retention of the political status quo and championed Austria and Russia, Prussia's partners in the Holy Alliance. Leopold's influence on policy increased rapidly after the accession of Frederick William IV (1840). From 1848 to 1854 Gerlach was at the height of his power. Made adjutant general in 1850, he was the moving spirit of the court camarilla, which opposed the German revolution, persuaded the Prussian monarch to refuse the crown offered by the Frankfurt assembly, and attempted to channel the 1850 constitution into a more conservative direction. Despite his friendship with Russia, he advocated a policy of strict neutrality during the Crimean War (1854–56). Leopold died eight days after his sovereign.