Defendu is a martial art that was created by British police officers and servicemen. Its inception occurred in the early 20th century, specifically during the period of World War II.

The primary objectives behind the development of Defendu were self-defense and close combat, with an emphasis on functionality, efficiency, and practicability. Numerous martial arts are incorporated into the Defendu system of techniques, such as jujitsu, boxing, wrestling, and stick combat.

Its emphasis on swift, innate reactions and methodologies customized for practical combat situations rendered it notably beneficial for law enforcement officers and military personnel. Defendu is frequently linked to the training of Allied forces by Fairbairn and Sykes during World War II, particularly their contributions to the British Commandos and the Office of Strategic Services (OSS), an American organization that served as the forerunner to the CIA.

Manuals authored by Fairbairn and Sykes regarding self-defense and close combat techniques were also extensively utilized by law enforcement and military personnel. Although Defendu is not as prevalent in contemporary martial arts as other styles, its enduring impact remains evident in numerous contemporary self-defense systems and military combatives programs.

By incorporating Defendu's principles into other self-defense and martial arts systems, their practical efficacy has been enhanced. .