In 1629 he was promoted to Lieutenant-colonel in the "Nylands och Tavastehus" Cavalry regiment, leading Finnish horsemen, also known as "Hakkapeliitat", for the first time into the Thirty Years' War. At the Battle of Breitenfeld (1631) they rode with the right wing personally led by King Gustavus Adolphus. In 1632 he was promoted to the rank of Colonel. At the siege of Nuremberg he assaulted the "invincible warriors" of Austrian Colonel Cronberg and, thanks to his mighty and successful charges, largely determined the outcome of the Battle of Lützen, where Gustavus Adolphus was killed, the battle was nonetheless won.