The Spitfire had met its match in the Focke-Wulf Fw 190, and by the middle of 1942, the Royal Air Force was looking for ways to improve its workhorse to match. Engineers at Rolls-Royce met the challenge with an improved Merlin engine with a two-stage supercharger while the masterminds at Supermarine worked diligently on improved airframe designs. Eventually, those would lead to the Griffon-powered Spitfires. In the interim, the Spitfire Mk.IX spanned the gap between the Mk.Vb and the Mk.VII and Mk.VIII designs—yes, they are not in chronological order! The first Mk.IX was an upgraded Mk.Vc that incorporated the Merlin 61, improving the fighter’s performance at high altitudes and increasing its top speed and climb rates. Although it didn’t have the strength improvements of the later variants, the stopgap Spitfire Mk.IX became the second most numerous variant, helped keep Britain in the air war, and made a worthy foe for the Fw 190.