Defendo is a Canadian military martial art and a self defence system created during WWII for law enforcement structures by veteran instructors.

Combato had its beginning in the Liverpool theatres with jujutsu demonstrations by travelling Japanese wrestlers, Yukio Tani and Taro Miyake.

[2] From 1969 to his death on February 8, 1986, in Newmarket, Ontario, Underwood was well known for his system and honoured and profiled frequently by the North American media.

In 1980 a short documentary film about Underwood's life and work, entitled Don't Mess With Bill was nominated for an Oscar at the 53rd Academy Awards in 1981.

He also appeared at that time on all of Hollywood's major talk shows including Real People, That's Incredible, and Merv Griffin; on all occasions, promoting and teaching his system of Defendo.