In 1922, the United States Army took delivery of its first helicopter – the de Bothezat Flying Octopus. Few inventions in history are truly revolutionary breakthroughs – most are incremental developments proverbially standing on the shoulders of giants. While the first successful helicopter to enter US Army Air Force service was the Sikorsky R-4B Hoverfly in World War II, it was far from the first helicopter purchased by the Army. In fact, US Army aviation dates back to the Union Balloon Corps of the Civil War.