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.

Every major country quickly established national broadcasting networks. In the United States such networks were privately owned and were financed by advertising, but in Europe the typical pattern was direct control by the government. In Great Britain, Parliament set up an independent public corporation, the British Broadcasting Corporation (BBC), supported by licensing fees. Whatever the institutional framework, radio enjoyed a meteoric growth in popularity. By the late 1930s more than three out of every four households in both democratic Great Britain and dictatorial Germany had at least one radio.

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.