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Radio began as a wireless communication system employed mainly for ship-to-ship and ship-to-shore communication and as a hobby for wireless enthusiasts. Before World War I, radio hobbyists built send-and-receive transmitters and communicated (first in Morse code, then in voice) with their associates in distant places. Although the ban on amateur broadcasting during the war temporarily slowed the nonmilitary use of radio, wartime training and technical advancements led to a boom in amateur interest in radio. By 1922 a sizable group of radio enthusiasts had developed. It included among its ranks both curious amateurs and individuals who worked for churches, stores, manufacturers—in short, any enterprise that had a message, commercial or otherwise, to deliver to the listening public.