The Rolls-Royce Merlin is a V12 liquid-cooled aircraft engine designed and produced by the famous Rolls-Royce company, then used by the British Republican Air Force during World War II. Such engines can produce from 1,730 to 2,420 horsepower. Its historical relevance lies in its adoption by iconic aircraft like the later variants of the Supermarine Spitfire, where it provided increased power and performance, though by the time it began mass production the dawn of jet fighters loomed in the horizon.