Born in Berlin to Jewish parents, Hahn attended school in the city, then universities at Oxford, Heidelberg, Freiburg and Göttingen.

Hahn was raised Jewish, and began his fierce criticism of the Nazi regime after the Potempa murder of 1932, when Stormtroopers attacked and killed a young communist in the presence of his mother.

After an appeal by the British Prime Minister, Ramsay MacDonald, Hahn was released and in July 1933 he was forced to leave Germany and moved to the United Kingdom.

Hahn relied here on Bernhard Zimmermann, the former Director of the Göttingen University Physical Education Department, who had to leave Germany in 1938 as he did not want to divorce his Jewish wife.

Hahn's educational thinking was crystallised by World War I, which he viewed as proof of the corruption of society and a promise of later doom if people, Europeans particularly, could not be taught differently.

At the Schule Schloss Salem, in addition to acting as headmaster, he taught history, politics, ancient Greek, Shakespeare, and Schiller.

[12] During his lifetime, Hahn summarised his beliefs about the younger generation at the time into six key points, describing them as the Six Declines of Modern Youth:[13][14][15][16] Hahn also proposed four solutions to these problems, all of which manifested themselves in a variety of ways at Salem, Gordonstoun, Atlantic College, and with Outward Bound: Kurt applied these seven laws to Salem School, Gordonstoun School, community programs for building physical fitness and social spirit, the worldwide Outward Bound movement and Atlantic College.

[18] In 1934, through his lectures in London to the New Education Fellowship, Hahn met the educationalist T. C. Worsley and persuaded him to spend a summer term at the newly founded Gordonstoun in the capacity of consultant.

[19] In his memoir Flannelled Fool: A Slice of a Life in the Thirties, Worsley records his impressions of Hahn's penetrating character analysis, and his energy and commitment in the cause of human development, but as time went on he became critical of Hahn's "despotic, overpowering personality":[20] He revealed himself as having a fierce temper, a strong hand with the cane, and a temperament which hated being crossed.