Close Quarters Combat (CQC), or World War II combatives, was largely codified by William Ewart Fairbairn and Eric Anthony Sykes. Also known for their eponymous Fairbairn-Sykes fighting knife, Fairbairn and Sykes had worked in the Shanghai Municipal Police of the International Settlement (1854–1943) of Shanghai in the 1920s, widely acknowledged as the most dangerous port city in the world due to a heavy opium trade run by organized crime (the Chinese Triads). CQC was derived from a mixture of judo, jujutsu, boxing, wrestling and street fighting.