In the summer of 1940 Germany continued the war in the sky of its great enemy; it was the "Adlertag", the operation which should have ensured three days of aerial supremacy to the Luftwaffe. It was the indispensable condition for the success of the "Seelowe" operation, the landing in England. Those were days of fierce fighting, which ended with the unequivocal victory of the Royal Air Force, favored without any doubt by the clumsy mistakes committed by the German. Anyway, it is irrefutable that if the British had not been in possession of a fighter aircraft like the Spitfire the events would have been probably different. Now let us see in detail the "Spit", as its pilots familiarly called it. The prototype of this prestigious fighter effectuated its first flight the 5th March 1936 and the serial production started in March 1937. At the outbreak of the war, nine squadrons were equipped with it; they could seem many as a starting point for the modernization of the Royal Air Force. Actually, the events rushed in such a way that, when the Battle of Britain started, the number of these fighters barely ensured a minimal aerial defense of the national territory. The Supermarine Spitfire was a monoplane aircraft fitted with low wings of characteristic elliptical shape, with the two parts of the body made of a light alloy. The engine rested on a structure of steel tubes in the fore part of the fuselage; the central part was coated with aluminum sheets of one millimeter in thickness, whereas the movable steering surfaces were coated with fabric. The pilot was protected by 33 kilograms of armored plates and a bulletproof windshield. The engine of the Mark I (that depicted in the illustration) was a Rolls Royce with cylinders in V and start up by cartridge. The Type A armament comprised eight Browning 7.7-millimeter machine guns, four of which were later replaced by two Hispano Suiza 20-millimeter cannons, forming so the Type B. Later there would be a Type C (four cannons and underwing hardpoints for bombs) and a Type E (two cannons and two 12.7-millimeter machine guns). It had, besides, a novelty: IFF, a device capable of distinguishing, by means of an automatic exchange of encrypted signals, whether an aircraft was a friend or an enemy, when, for any reason, the doubt arose. In the end, the Spitfire, which began to be used in 1939 in France, was rather long-lived, for the production, started in 1937, would not be discontinued until 1947. It would be used for the last time in 1953, in the Korean War.