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From 1920 to 1928, he worked as functionary of the Communist Youth Movement of Germany. In 1926 he joined the Communist Party of Germany. He studied at the Lenin School in Moscow. Back in Germany, the Communist Party was expelled after the Nazis gained power in 1933. Ackermann continued working for the illegal Communist Party.
From 1935 to 1937 he lived in Prague. During the Spanish Civil War, Ackermann was the leader of the Political School of the International Brigades. After staying a shortwhile, he went to Moscow and became editor of the German language newspaper "The Free Word".
In 1943 he became an active member of the Moscow based National Committee for a Free Germany (NKFD).
After World War II, he returned to Germany as head of the Ackermann Group, the groups sent by the Communist Party to lay the groundwork for the Soviet Military Administration in Germany in Saxony. He joined the East German Communist party, the Socialist Unity Party (SED). He was elected into the Central Committee and became a candidate member of the Politburo in 1949. From 1950 to 1954, he was a member of the People's Chamber.
From 1949 to 1953, he was the Deputy Minister of Foreign Affairs. After the arrest of the minister, Georg Dertinger, Ackermann served briefly as Minister of Foreign Affairs.
In 1953-1954, he was expelled from the Politburo and fired as minister because of "party-hostile activity."
In 1956 he was rehabilitated and worked for the State Planning Bureau.
In 1970 he was rewarded with the Patriotic Service Medal. Ill with cancer, he committed suicide in 1973.
- "Namensliste der drei KPD-Einsatzgruppen vom 27. April 1945" German Federal Archives. BArch NY 4036/517. Retrieved November 22, 2011 (German)