Complex sentence: Many more projects during the rapid industrialization of the 1930s, war-time and post-war periods were fulfilled on the backs of convicts, and the activity of Gulag camps spanned a wide cross-section of Soviet industry.
Split into simpler sentences: Many more projects during the rapid industrialization of the 1930s, war-time and post-war periods were fulfilled on the backs of convicts. The activity of Gulag camps spanned a wide cross-section of Soviet industry.