Complex sentence: From June 1916 to March 1919, he helped publish "Arbeiterpolitik", a weekly newspaper that propagated scientific socialism.He did illegal work in Berlin and Munich, where he was arrested in January 1918.
Split into simpler sentences: From June 1916 to March 1919, he helped publish "Arbeiterpolitik", a weekly newspaper that propagated scientific socialism. He engaged in illegal political activities in Berlin and Munich, where he was arrested in January 1918.