 The son of a Lutheran pastor, Fuchs attended the University of Leipzig, where his father was a professor of theology, and became involved in student politics, joining the student branch of the Social Democratic Party of Germany (SPD), and the Reichsbanner Schwarz-Rot-Gold, the SPD's paramilitary organisation. He was expelled from the SPD in 1932, and joined the Communist Party of Germany (KPD). He went into hiding after the 1933 Reichstag fire, and fled to the United Kingdom, where he received his PhD from the University of Bristol under the supervision of Nevill Mott, and his DSc from the University of Edinburgh, where he worked as an assistant to Max Born.
