Imagination is DARPA's greatest weapon. In 1958 the Defense Advanced Research Projects Agency (DARPA) was established to prevent technological surprises like the Soviet's launch of Sputnik 1. Its original mission still applies, with the added goal of creating technological surprises for US enemies. DARPA promotes radical innovation for national security by funding research and development programs that will provide technological advances for the military. It has had a hand in the development of stealth aircraft, unmanned aerial vehicles, and the Internet. The agency is the research arm of the US Department of Defense.