There was no money for him to progress to a university level education so after leaving secondary school he undertook an apprenticeship in technical drawing.
Sources are not unanimous on the date, but it seems most likely that following several year as an active member of the Young Socialists, it was in 1931, by now aged 23, that he joined the Social Democratic Party ("Sozialdemokratische Partei Deutschlands" / SPD).
In 1933 Karl Obermann emigrated via Belgium to Paris which was rapidly becoming a focus for growing numbers of exiled German communists and other left-wing activists.
Like many German political exiles, Karl Obermann was arrested and interred at Camp Vernet in the far southwest of the country.
Whether he was formally released or simply walked out of the camp gates, in 1941 Obermann managed to escape from France to the United States of America.
[2] He was able to do this on a ship sailing from Marseilles, a well worn channel for German refugees, not yet fully closed off by the French authorities, which avoided the visa issues involved in trecking across Spain and Portugal.
Early on he became a member of the Socialist Unity Party ("Sozialistische Einheitspartei Deutschlands" / SED) which had been created under contentious circumstances in April 1946 and which, by the time the Soviet occupation zone was relaunched as the Soviet sponsored German Democratic Republic in October 1949, was emerging as the ruling party in a new kind of German one-party dictatorship.
[2] Further promotion followed in 1956: between 1956 and 1970 he served as a full professor ordinarius with a teaching chair, still at the Humboldt in Berlin, where in 1956 he was also appointed the first director of the newly formed Historical Institute of the (East) German Academy of Sciences and Humanities.
[1] He belonged to numerous national and international academic committees, notably of the East German Historical Association.