The British Supermarine Spitfire was facing several challenges by mid-1942. The debut of the formidable Focke-Wulf Fw 190 in late 1941 had caused problems for RAF fighter squadrons flying the latest Spitfire Mk Vb. By this time Rolls-Royce engineers were already working on a new version of the Merlin incorporating two-stage superchargers; the combination of the improved Merlins and the Spitfire Mk VC airframe in a "stop-gap" design allowed the RAF to combat the Fw 190 on equal terms. In a second stream of development Supermarine was working on an improved, reinforced Spitfire airframe which incorporated several new features and was designed specifically for the Merlin 60 and 70 series engines. This new airframe later formed the basis for the Rolls-Royce Griffon powered Spitfires.

This article presents a history of the Spitfire powered by two-stage engine variants and also describes some of the "drawing board" projects and experimental Spitfires. The Griffon powered variants are described in a separate article

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Supermarine Spitfire Mk.IX, USAF, Lt.Fred Ohr, 2nd Fighter Squadron, 52nd Fighter Group, Palermo, Sicily, August 1943.
Supermarine Spitfire Mk.IX, USAF, Maj.Garth Jared, 309th Fighter Squadron, Sothern Italy, November 1943.
Supermarine Spitfire Mk.IX, USAF, Lt.John Fawcett, 309th Fighter squadron, 31st Fighter Group, 15th Air Force, Castel Volturno, Italy, March 1944.
Supermarine Spitfire Mk.IX, RAF, Capt.F.S."Gabby" Gabreski, No.315 "Deblinski" Squadron, Northolt, Februari 1943.
Supermarine Spitfire Mk.IX, USAF, Lt.Vic Cabas, 4th Fighter Squadron, 52nd Fighter Group, Le Sers, Tunisia, Apri l 1943.

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