Like film, radio became a full-blown mass medium in the 1920s. Experimental radio sets were first available in the 1880s. The work of Italian inventor Guglielmo Marconi (1874–1937) around 1900 and the development of the vacuum tube in 1904 made possible primitive transmissions of speech and music. But the first major public broadcasts of news and special events occurred only in 1920, in Great Britain and the United States.

Like the movies, radio was well suited for political propaganda and manipulation. Dictators such as Hitler and Italy’s Benito Mussolini controlled the airwaves and could reach enormous national audiences with their dramatic speeches. In democratic countries, politicians such as American president Franklin Roosevelt and British prime minister Stanley Baldwin effectively used informal “fireside chats” to bolster their popularity.