Rolls-Royce Merlin

The Merlin was the engine of British victory in the air. A 27-litre liquid-cooled V12 first run in 1933, it grew from around 1,000 hp in its earliest marks to more than 2,000 hp by the end of the war, the later 60-series gaining a two-stage, two-speed supercharger that transformed high-altitude performance. It powered the Spitfire and Hurricane through the Battle of Britain, the de Havilland Mosquito, and — in four-engined form — the Lancaster and the later marks of Halifax; fitted to the North American Mustang it turned a mediocre fighter into the finest long-range escort of the war. Some 168,000 were built, including more than 55,000 made under licence in the United States by Packard as the V-1650.