He was a committed communist, and appalled by the 1936 Olympic Games that were to be held in Nazi Germany. He had originally planned to boycott it, but friends persuaded him to compete anyway, win, and defy the Nazis by not giving the required "Heil Hitler!" salute, but to use a vulgar gesture instead. This plan was foiled when he lost the first match. He eventually came fourth in the event.
He was arrested in 1942 and beheaded in 1944, in Brandenberg concentration camp, for supposed treason.
A number of schools and sporting facilities in the former East Germany were named after him, and since he died before the GDR was founded, still are today.