Based on Part II’s examinations regarding the period of the Second Reich, Part III analyzes business management during the Weimar period. Chapter 7 explores enterprise concentration and its special function in business management. It first examines the historical background of the concentration of enterprises in the wave of mergers called “the Second enterprise concentration.” Next, it considers the development of trust and the division of labor in production within the merged enterprise using two representative cases in the iron and steel and chemical industries. Based on the cases of Vereinigte Stahlwerke AG and IG Farbenindustrie AG, this chapter analyzes how reducing excessive production capacity and reorganizing the division of labor in the production system was implemented using fusion. These examinations clarify the characteristics and significance of enterprise concentration in this period for the subsequent rationalization process.