 Kessler was promoted from Chief of the Main Political Administration "(Chef der Politischen Hauptverwaltung)" of the NVA to Defense Minister (with the rank of "Armeegeneral") on 3 December 1985 after his predecessor, "Armeegeneral" Heinz Hoffmann, died of a heart attack.In 1991, after the Unification of Germany, Kessler was arrested after police received information that Kessler would attempt to flee the country disguised as a Soviet officer.German police blockaded the Sperenberg Airfield to prevent Kessler's escape, but later arrested him in Berlin after changing the lock on his home and informing him that he could retrieve his keys at a local police station.