[1] During the postwar period, in what had become the Soviet occupation zone, he was a co-founder, in 1948/49, of the anti-communist Combat Group against Inhumanity ("Kampfgruppe gegen Unmenschlichkeit").
The political backdrop changed savagely in January 1933 when the Nazi Party took power and converted Germany into a one-party dictatorship.
[5] During the twelve years the Nazis were in power, Birkenfeld (as he later explained to Alfred Kantorowicz [de] in 1947) managed to carry on in what was termed inner emigration in a low profile lectureship, also producing several popular biographical novels including one on Johann Gutenberg and another on the emperor Augustus.
For Weisenborn this meant that despite recent reproaches to Thomas Mann, the author should nevertheless be invited to the 1947 writers' congress; Birkenfeld rejected this.
This followed consultation with PEN International's General Secreatary Hermon Ould, and with Wilhelm Unger representing the London exile group.
As it became apparent that the ground was being cleared, especially within the Soviet occupation zone, for a return to one-party dictatorship under the Socialist Unity Party of Germany, Birkenfeld was taking am increasingly public position against Communism, at least from the launch of the Berlin Blockade in June 1948, and possibly earlier.
At Suhrkamp he became embroiled in controversy when he demanded that the author Anna Seghers should at least mention somewhere in her novel Die Toten bleiben jung that German soldiers involved in the invasion of the Soviet Union had not been universally hostile to the civilian communities - there had been some who had befriended the population.
In the dispute that ensued, the proprietor Peter Suhrkamp distanced himself from Birkenfeld's demands, and it was left to the company's publishing director Erich Wendt [de] to negotiate a solution with a determined author.