After the end of World War II, Kahn learned his parents had perished in the Holocaust, which was a traumatic experience that caused him to lose his faith.

After internment as an enemy alien on the Isle of Man and in Quebec, Canada, he was able to study at Dalhousie University with the help of a Halifax couple.

Kahn's research interests were German literature in the Age of Goethe and Romanticism, and he was one of the editors of Georg Forster's works.

[6] Kahn's parents moved to Leipzig, which had a large Jewish community, as life in Nuremberg was becoming increasingly unbearable for Jews.

[10] Following the mass arrests after Kristallnacht in November 1938, Gustav Kahn was imprisoned at Buchenwald and Sachsenhausen concentration camps,[3][7] and released again in February 1939.

[12] He studied at Dalhousie University and obtained his BA in 1944 and his MA (in history and philosophy) in 1945, his thesis titled Goethe and the French Revolution.

[20] In February 1970, Kahn was offered a professorship at the University of Florida, but declined the post because he felt he could not leave his students at Rice.

[27] Kahn's students include Wolfgang Justen, Marianne Kalinke, Hanna Lewis, Gertrud Bauer-Pickar, and Egon Schwarz [de].

[28] After World War II ended, he learned that both of his parents had perished in the Holocaust either by suicide or after deportation to an extermination camp: Kahn's father died on March 27, 1942,[3] ingesting sleeping pills[28] when the Nazis had taken his two sisters.

[16] His widow later described Kahn's "deep depression" as related to two great disappointments: the lack of success of his poetry and strong disagreements with his colleagues, and stated he was torn between feelings of love (especially for his mother), hate, and guilt.

ein zyklus, described as reminiscent of Paul Celan's Todesfuge,[34] was broadcast on the German radio station Saarländischer Rundfunk in 1968.

[22] Kahn was invited to the 1966 meeting of Group 47 in Princeton[35] and read some of his poems there with other authors including Erich Fried, Günter Grass, and Walter Jens.