Propaganda is presenting information to influence the audience's attitude or convictions. Although it has existed since the most ancient times, it was in the late 19th century when Propaganda was codified, primarily by Gustave Le Bon in 1897. Some of the most notable uses of Propaganda throughout the 20th century were The Creel Committee in the US (to promote joining the WW I at Britain's side), the Soviet "Voice from the sky" (a large plane that served as a mobile propaganda center) and Leni Riefenstahl's works in Nazi Germany.