At first Hahn wanted to be an art teacher in his native Bohemia, but he broke off his studies in order to dedicate himself entirely to art. In 1937 he went to Prague to study painting at the academy of arts. Not long afterwards the Nazis seized power in Czechoslovakia. Two months before the outbreak of war Hahn fled to England. As a Jew, he was in direct danger. He worked in England as a factory worker and on a farm. Hahn received an American visa shortly before the end of the war in 1945 and left for the United States. He thereby broke off his art studies in Oxford, which he had only been only able to find sponsors for in 1944.

His childhood friend Olga Kleinmünz was waiting for him in New York. They had not seen each other for seven years. His start in the US was promising: Hahn attended drawing classes at the Art Student League to receive further training as an artist. His wife supported him in his endeavours. She had found work as a fashion illustrator, which secured them a livelihood.

In 1949 Olga fell ill with multiple sclerosis. Hahn had to put his career plans on hold and earned money retouching photographs. His profession and caring for his wife left him little room for his own art for many years. The high standards he held for himself and his work meant that in the end he only produced a small body of work.

Selected works:
Gedichte und fünf Zeichnungen (1987)
Eklipse und Strahl (Gedichte und Zeichnungen, 1997)
Holocaust Poems 1965 – 1975 (Gedichte, 1998)
Die Doppelgebärde der Welt (Gedichte, Prosa, Zeichnungen, 2004)