Shanghai in the 1920s and 1930s was troubled by powerful criminal gangs run by ruthless godfathers; the most powerful of who were Du Yuesheng; known as Zongshi or 'The Boss' of the Green Gang and the Shanghai underworld; Zhang Xiaolin; also a powerful Green Gang leader; and Huang Jingrong; the highest-ranking Chinese detective on the French Concession Police (FCP) and one of Shanghai's most important gangsters.

Their empires included drugs; protection rackets; smuggling and prostitution.