Lestwitz began his military career in 1734 as a "Fahnenjunker" in the infantry regiment of Kurt Christoph von Schwerin in Frankfurt on the Oder. In the First and Second Silesian Wars, Lestwitz participated in some of the most hotly contested battles: Mollwitz, Chotusitz, Hohenfriedberg, and Soor. In the Seven Years' War, after the Battle of Lobositz (1 October 1756), he received the Order Pour le Mérite.