The Mosquito was the most successful battle-winning multi-role combat aircraft of the Second World War. It was introduced by the de Havilland Aircraft Company as an unarmed, un-interceptable, long range, high speed, high altitude medium bomber. An unarmed bomber without protective armament was a concept that ran directly contrary to the tactical doctrines of both the Royal Air Force and the US Army Air Force. Notwithstanding, it was developed to carry out almost unlimited roles including ground-