During World War II, radio was recognised globally as an essential propaganda machine used by all sides. At the time in Finland, one particular radio programme, Jahvetin kirjelaatikko (Jahvetti’s Letterbox), aimed to discuss and resolve citizens’ everyday worries and to simultaneously utilise a network of secret proxies who could gather information about and help to manipulate public opinion. Javetti’s Letterbox came to be the most popular broadcast in Finland during the so-called Continuation War of 1941-1944 against the Soviet Union and provides evidence of radio’s power in information warfare where citizens’ trust in Finland’s battle was at stake.