 Upon the sudden death of Paul Siebeck, in 1920, Oskar and his brother, Werner Siebeck, took the helm.In the wake of crisis, caused by a reduction in funding for science and education and by Hyperinflation in the Weimar Republic, the program streamlined, specializing in the four core subjects of theology, philosophy, law, and economics – which remain its focus today.Following the Nazi seizure of power and rise of Nazism, the publishing program of Mohr (Siebeck) – with its numerous Jewish and left-leaning authors – was no longer popular politically, with sales sinking down to one-tenth.