In 1945 Kessler returned to Berlin and became a leading figure in the communist Free Democratic Youth organization. During 1950–1955 he served in high military positions in the East German military. Trained at the Soviet Air War Academy, Kessler was promoted to deputy minister for national defense and commander, as a lieutenant general, of the East German Air Force in 1957. In 1967 he became chief of staff of the National People's Army and in 1979 chief of the Army's Political Main Department. During all his assignments, he continued to serve as a deputy minister for national defense.
Kessler was a close confidante of East German head of state Erich Honecker, and after Heinz Hoffmann's death in 1985, Kessler was named minister for national defense and was promoted to the rank of full general. He also joined the East German politburo as a full member in 1985.
In November 1989, as the Velvet Revolution rippled throughout Eastern Europe and the Berlin Wall was being torn down, Kessler was forced to resign from his leadership posts. After German unification in October 1990, he was put on trial for authorizing the shootings of East Germans attempting to escape East Germany and in 1993 was sentenced to seven years in prison. In October 1998 he was released on parole for medical reasons. He now lives a sequestered life in Berlin.
Kessler, Heinz. Zur Sache und zur Person. Berlin: Edition ost, 1996.