During the First World War Augspurg and Heymann held illegal gatherings in their Munich apartment. They participated in the International Congress of Women in The Hague, Netherlands, in April 1915, which led to the founding in 1919 of the Women's International League for Peace and Freedom (IFFF), of which Heymann was Vice President. They found a common anti-war ground with the Independent Social Democrats, which had split off from the Social Democratic Party. In this context, their former differences with Socialist women such as Clara Zetkin became less important. Augspurg collaborated with Kurt Eisner, and after the proclamation of the Weimar Republic in 1918, became a member of the provisional Landtag of Bavaria. In following elections they soon ran on the list of Independent Social Democrats, but gained no mandate.