The P-47D was the first version of the Thunderbolt to undergo a large-scale
production. Demand for the Thunderbolt was so
great that Republic built a new factory at Evansville, Indiana to augment
production of the P-47D in the 1940s.
The first P-47Ds were actually the same as P-47Cs. Other P-47D variants successively incorporated changes such as the addition of more engine cooling flaps around the back of the cowl to reduce the engine overheating problems that had been seen in the field. Engines and engine subsystems saw refinement, as did the fuel, oil and hydraulic systems.
Thunderbolt, thus, was among the production
versions that have more powerful engines, giving a maximum speed of 470 mph (756 km/h), and additional armor protection for the pilot. These versions were used for anti V1 Flying Bombduties. They served in every active combat theater and with many Allied air forces.