The regiment was a part of a small army raised by Bernhard of Saxe-Weimar in 1631 to help Gustavus Adolphus against the emperor during the Thirty Years' War. The regiment fought together with the Swedish Army at Breitenfeld, Rain and Lützen. With the death of Gustavus Adolphus and the disaster at Nördlingen the army of Bernhard of Saxe-Weimar entered French service on 26 October 1635. During this time the regiment was commanded by Colonel Trefsky and carried his name: "Trefsky-Cavalerie" (Trefsky Cavalry).