During the five years of the Second World War, the power of engines and speed of aircraft increased as much as it did during twenty years of peacetime. Conventional aircraft and engines reached the limits marked in the original design and surpassed them, very fast. The basis for this huge achievement was exotic fuels, short-lived artificially overpowered engines, propellers with four, five, and even six blades, and thinner wings with special sections of laminar flow. Then the faster Allied fighters began to be attacked by a demon that lived in the air: scientists called it compressibility buffeting and different type of aircraft suffered it at different speeds and manifested itself in different ways. The American and British designers never understood the true causes behind the aerodynamic phenomenon. They were forced to adopt brute force solutions by increasing engine power on the turbojet powered fighters, leaving in the background the research on the last projects of fighters, driven by monster piston engines. The purpose of this book is to present them to the public, for its notable interest.