The Besa Machine Gun was a British version of the Czechoslovak ZB-53 air-cooled, belt-fed machine-gun, which in the Czechoslovak army was marked as the TK vz. 37. It was used extensively by the armed forces of United Kingdom during the Second World War, as a mounted machine gun for tanks and other armoured vehicles, to replace the heavier, water-cooled Vickers machine gun. Although it required a rather large opening in the tank's armour, it was dependable and reliable. The name came from the Birmingham Small Arms Company (BSA), who signed an agreement with Československá zbrojovka to manufacture the gun in the UK. The War Office ordered the weapon in 1938, and production began in 1939, after modifications.