The U.S. Treasury attaché in Shanghai in 1934, just three years after the League of Nations had imposed restrictions on the manufacture of heroin in Europe, notes a sudden shift of the traffic in narcotics from Europe to the Orient

According to his report, after the annual harvest in the southwestern highlands at least eighteen thousand tons of Sichuan and ten thousand tons of Yunnan opium passes through the major river ports downriver to Shanghai.

He reports that China's Opium King is Green Gang leader Tu Yueh-shen, whose close relations with the Nationalist regime makes his cartel a major force in the Yangtze River opium trade that dominates China's drug traffic.