There, he joined the Sozialistischer Deutscher Studentenbund (Socialist German Student Association) in the wake of the shooting of Benno Ohnesorg by the police.

Under the influence of his party he gave up his 1974 doctoral dissertation, preferring instead to devote himself to the "revolutionary factory work" and from 1976 to edit the Communist People's Daily of KBW.

[1] Koenen's 2001 book Das rote Jahrzehnt ("The Red Decade") became well-known and due to the discussion of the radical leftist past of foreign minister Joschka Fischer, and the importance of the '68 movement in the history of the Federal Republic.

In a 2001 edition of the Joscha Schmierer-edited magazine Commune, Koenen inveighed against the "trial of the young seniors of the Free and Christian Democracy, a rhetoric of universal suspicion of their way of Resolute conformism as the only possible way of socialization ex post yet to establish".

Koenen got his doctorate in 2003 from the University of Tübingen with his thesis Rom oder Moskau – Deutschland, der Westen und die Revolutionierung Russlands 1914–1924 ("Rome or Moscow: Germany, the West and the revolutionization of Russia 1914–1924").