Fairbairn was a Royal Marine Soldier who is credited as the pioneer of modern close quarters combatives. In 1907, Fairbairn joined the Shanghai Municipal Police and served as the Primary Chief CQC instructor - Shanghai was considered to be the most dangerous city in the world at the time. Fairbairn founded and trained the Shanghai Reserve Unit (the Riot Squad) — which is the first Special Weapons & Tactics Unit in the world, and became the precursor for modern S.W.A.T. and S.R.T. teams. In China, Fairbairn studied and became proficient in Baguazhang under the instruction of Tsai Ching Tung (Cui Zhendong, Bagua student of Yin Fu), who was employed at the Imperial Palace, Beijing, as the instructor to the Retainers of the late Empress Dowager. Fairbairn later made a dedication in his book All In Fighting/The Fairbairn Method (1942) to Cui Zhendong calling him a man of "terrifying prowess." Around 1939 during the start of World War II, Fairbairn was recruited to train British Commandos and Special Operations in close quarters combative and edged weapon strategy. He integrated elements of Baguazhang's ox tongue-dragon claw hand shape/strikes/biomechanics and knife concepts into the combat training program, also designing the Fairbairn-Sykes fighting knife issued to the British Commandos and SAS. OSS Agents (predecessor of the modern Central Intelligence Agency (CIA), Federal Law Enforcement (FBI), received elite combative training from William Fairbairn as well.