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>Pretty much all piston driven war planes were turbocharged
Actually, I think more aircraft were *super*charged than *turbo*charged. The Merlin engine, for example, used on Spitfires and Mustangs, was supercharged. Turbochargers were more rare because they required extensive ducting (as is obvious in the OP photo) whereas superchargers basically bolt on to the back of the engine. Turbos are more expensive too, since they need high-temperature alloys in the turbo to deal with the hot exhaust gasses.
But yeah, naturally aspirated engines were a rarity.
Without a compressor, a piston-engine doesn’t work very well above 10 or 12 thousand feet because there’s insufficient air mass in the cylinders. At 30,000 feet, a naturally-aspirated engine rated for 1000hp at sea level is outputting about 300hp. With a compressor you can bring it back up to 1000hp.