He was appointed member of the Royal Council in 1625, Field Marshal in 1628, Governor General of Livonia in 1652 and Lord High Constable since 1653. In the Thirty Years' War (1618–1648), he was instrumental as a commander in securing victory at the Battle of Breitenfeld, in 1631. He was High Councillor of the realm in 1625, elevated to the rank of field marshal in 1628, and sometimes commander-in-chief of Swedish forces in Germany during Thirty Years' War. After the war, he served as Governor-General of Livonia 1652, President of War department and Lord High Constable in 1653. In 1651, Queen Christina created him Count of Björneborg ("Horn af Björneborg").