William E. Fairbairn https://en.wikipedia.org/wiki/William_E._Fairbairn (Wikipedia).
It is stated he joined the Shanghai Municipal Police (SMP) in 1907. During his service with the International Police in Shanghai, Fairbairn reportedly engaged in hundreds of street fights in the course of his duties over a twenty-year career, where he organised and headed a special anti-riot squad. Much of his body, arms, legs, torso, even the palms of his hands, were covered with scars from knife wounds from those fights.  Fairbairn later created, organised, and trained a special anti-riot squad for the Shanghai police force. He also developed numerous firearms training courses and items of police equipment, including a special metal-lined bulletproof vest designed to stop high-velocity bullets from the 7.63x25mm Mauser pistol.

W E Fairbairn's first book "Defendu. Scientific Self-Defence" was published in Shanghai in 1926. He wrote other books on self defence in the 1930s and 1940s. During the Second World War he trained Commandos in close-combat, pistol-shooting and knife-fighting techniques.