The Birmingham Small Arms Company has a long history as a firearms manufacturer and was also well-known as the world"s largest motorcycle manufacturer during WWII. In 1939, BSA began production of a military version of their M20 commercial motorcycle that was fitted with a Lucas light and other additional equipment. It was powered by a 12hp single-cylinder 500cc side-valve engine and offered superb reliability and ease of maintenance. Modifications were made during the course of the production and late-war motorcycles featured an air filter fitted onto the fuel tank.
 
Over 126,000 units were produced during the war and most of them were deployed with the British Army. They saw service on every front for a wide range of duties including liaison and supply convoy escort. Some were also used by the RAF and British Navy. After the war, the M20 continued to serve throughout 1950s and some were even used until the end of the 1960s