Fairbairn was called upon by the British to help train Allied troops in World War II. Fairbairn and others expanded on this system to create the Close Quarters Combat system that was then taught to the troops. This system was built on Defendu, but modified for military applications, rather than police and riot control.
The original Defendu was oriented towards self-defence and restraint, while the Close Quarters Combat system concentrated on rapid disabling of an opponent, with potentially lethal force. The militarised version of Defendu is described in the military manual All in fighting 1942, used as a supplement during WW2 CQB-training. This book was later published in a civilian edition, missing the chapters on bayonet-fighting and rifle sighting, under the name Get Tough! How To Win In Hand-To-Hand Fighting. As Taught To The British Commandos And The U.S. Armed Forces. Fairbairn's CQC-system is also described in Rex Applegate's book Kill or Get Killed.
Publications:
Defendu
Scientific Self-Defence
All-In Fighting
Get Tough
Hands Off! (Self Defence for Women and Girls)
Shooting to Live
All of Fairbairn's works are published and available from The Naval & Military Press.