Frederick had a successful military career in the Swedish army, where he made it to the Major General. It is unknown whether he was active during the Thirty Years' War. During the Second Northern War, he commanded a Swedish battle group. Due to his military career, he spent much time at the Swedish court and rarely visited Eschwege. His three brothers ruled his share of the Rotenburg Quarter on his behalf. Even so, he cared about his subjects and contributed significantly to the reconstruction after the end of the Thirty Years' War. His wife mostly stayed in Eschwege and his children were born there.