The Spitfire Mk.1 first became operational in July 1938 at Duxford, Cambridge. At the beginning of WWII 9 RAF squadrons were equipped with the Mk.1’s with two others converting to the new aircraft. By June 1940 the Mk.1 was being replaced by the faster long-range Mk.II but not before the Mk.I had bore the brunt of the Battle of Britain. The Mk.I also flew protective cover over the evacuation of Dunkirk. The Mk.1A had 8 machine guns instead of 4, a bulged canopy, a 3-blade propeller, self-sealing fuel tanks, armored windscreen and armor plating in front of and behind the pilot.