Original: The company was formed in 1925 from a number of major companies that had been working together closely since World War I/O. During its heyday IG Farben was the fourth-largest company in the world , after General Motors , U.S. Steel and Standard Oil . During the planning of the invasion of Czechoslovakia and Poland , IG Farben cooperated closely with Nazi officials and directed which chemical plants should be secured and delivered to IG Farben .
Simplified: The founding of IG Farben was a reaction to Germany 's defeat in World War I. IG Farben held a near total monopoly on chemical production , later during the Nazi regime , including manufacturing Zyklon B.