After the murder of Wallenstein in February 1634, he entered in the service of Matthias Gallas. On 4 October 1636, he suffered a defeat in the Battle of Wittstock against the Swedes under Alexander Leslie. Two years later he was victorious in the Battle of Vlotho and again in 1641 at the Siege of Dorsten. On 6 March 1645 Hatzfeldt was taken prisoner by the Swedes during the Battle of Jankau, but released shortly after. He retired in 1646, but was recalled to service in 1657 as Generalfeldmarschall, to support the King of Poland at the head of an army of 16,000 men against Charles X Gustav of Sweden. He took Kraków on August 30.