From the outbreak of war in 1939, German Luftwaffe armament designers and technicians pioneered many revolutionary concepts in the barrelled armaments of their military aircraft, particularly as the threat posed by the combined US and British Allied strategic bombing campaign grew in intensity from 1943. Desperate solutions were sought in an effort to counter the threat posed by Allied bomber aircraft to German industry and infrastructure, which in turn saw the introduction into service of airborne guns with ever-increasing calibres and impressive levels of lethality. This book examines the use of the humble rifle calibre machine gun as an aircraft weapon along with the efforts to develop suitable cannon with greater destructive power for aircraft use, the advances made during the inter-war years and the various barrelled weaponry either used or proposed by the German Luftwaffe in the Second World War. This work encompasses not only the technical and operational appraisals of the various weapons used by the German Luftwaffe aircrews, which include some of Germany's leading surviving fighter aces of the Second World War, but also the armourers tasked with their day-to-day maintenance, the instructors and technicians on the ground, and those who found themselves at the receiving end of their firepower both in the air and on the ground. This unique work encompasses many new and previously unpublished testimonies as told by those who were there in their own words and for the first time.