Throughout its entire 14-year existence, the Weimar Republic remained under threat of militaristic nationalism, as many Germans felt the Treaty of Versailles humiliated their militaristic culture. The Weimar years saw large-scale right-wing militarist and paramilitary mass organizations such as "Der Stahlhelm" as well as illegal underground militias such as the "Freikorps" and the Black Reichswehr. Formed as early as 1920, out of the latter two soon rose the "Sturmabteilung" (SA), the paramilitary branch of the Nazi party. All of these were responsible for the political violence of so-called "Feme" murders and an overall atmosphere of lingering civil war during the Weimar period. During the Weimar era, mathematician and political writer Emil Julius Gumbel published in-depth analyses of the militarist paramilitary violence characterizing German public life as well as the state's lenient to sympathetic reaction to it if the violence was committed by the political right.