Frederick Michael was Palatine Fieldmarshal, Governor of Mannheim and finally in 1758 as Fieldmarshal of the Holy Roman Empire commander-in-chief of the Reichsarmee in the Seven Years' War against Frederick the Great. After the Battle of Rossbach, he managed to build up the whipped imperial army again, for which he received the Grand Cross of the Military Maria Theresa Order. In the fall of 1758 he invaded Saxony, took the fortress Sonnenstein and besieged Leipzig. The following year, Leipzig, Torgau, Wittenberg and Dresden were conquered. He secured Marshal Daun in the Battle of Maxen and fought victorious in the battle of Strehlen. 1761, he resigned from his post and handed over the imperial troops to Field Marshal Johann von Serbelloni.After the peace of Hubertusburg Friedrich Michael received the General Command in Bohemia and later became president of the secret military conference.