In 1777 he joined the Savolax Brigade protecting the Finnish border against Russian aggression. Adlercreutz first saw action in the 1788-1790 Russo-Swedish War, where he distinguished himself. He was promoted Major in 1791 and Squadron Commander 1792. During the Anjala mutiny he remained faithful to the King, standing against the war with Russia, then took part in the trials against the conspirators. He was thereafter appointed the commanding officer of the Nyland Dragoons, holding this post until 1804, when he was made "Ofverste" (Colonel-in-Chief) of the newly raised Adlercreutz Regiment.