Lieutenant Colonel William Ewart Fairbairn was a British soldier and police officer. He developed hand-to-hand combat methods for the Shanghai Police during the interwar period, as well as for the Allied special forces during World War II. He created his own fighting system known as Defendu. Notably, this included innovative pistol shooting techniques and the development of the Fairbairn–Sykes fighting knife.

The Fairbairn–Sykes fighting knife is a double-edged fighting knife resembling a dagger or poignard with a foil grip. It was developed by William Ewart Fairbairn and Eric Anthony Sykes in Shanghai based on ideas that the two men had while serving on the Shanghai Municipal Police in China before World War II.