The Republic P-47 Thunderbolt was one of the largest and heaviest fighter aircraft in history to be powered by a single piston engine. It was heavily armed with eight .50-caliber machine guns, four per wing. When fully loaded, the P-47 weighed up to eight tons, and in the fighter-bomber ground-attack roles could carry five-inch rockets or a significant bomb load of 2,500 pounds; it could carry more than half the payload of the B-17 bomber on long-range missions (although the B-17 had a far greater range). The P-47, based on the powerful Pratt & Whitney R-2800 Double Wasp engine — the same engine used by two very successful U.S. Navy fighters, the Grumman F6F Hellcat and Vought F4U Corsair, itself the first to fly with Double Wasp power in late May of 1940 — was to be very effective as a short-to-medium range escort fighter in high-altitude air-to-air combat and, when deployed as a fighter-bomber with its usual "double quartet" of heavy-calibre M2 Browning machine guns, proved especially adept at ground attack in both the World War II European and Pacific Theaters.
The P-47 was one of the main United States Army Air Forces (USAAF) fighters of World War II, and served with other Allied air forces, notably those of France, Britain, and Russia. Mexican and Brazilian squadrons fighting alongside the U.S. were equipped with the P-47.
The armored cockpit was roomy inside, comfortable for the pilot, and offered good visibility. A modern-day U.S. ground-attack aircraft, the Fairchild Republic A-10 Thunderbolt II, takes its name from the P-47. Orders for an additional 5,934 were cancelled when the war ended.