Attempts to create helicopters can be traced back to Leonardo da Vinci, but the first working prototype helicopter, the VS-300, was invented by Igor Sikorsky in 1939. The next model he designed was the R-4 in 1942, which was the world's first mass produced helicopter. Sikorsky pioneered the rotor configuration that is used on most modern helicopters.
By the end of World War II, most modern countries had helicopters. Once Sikorsky began to produce his model, the Germans and Russians were quick behind him to make their own type of helicopter. The R-4 model created by Sikorsky was the only model to serve in World War II. It was used as a direct lift aircraft to rescue people trapped in areas inaccessible by planes.