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.