The state of Irish opinion was a matter of some importance to British military and intelligence chiefs. It would determine the number of Irish people willing to assist the Axis and the type of reaction the British would receive if they were forced to intervene in southern Ireland. The study of opinion inevitably led to the question of propaganda. The Second World War saw unprecedented efforts by governments to assert control over information and public opinion. They used ‘white’ propaganda techniques – the manipulation of news to extol their cause; and ‘black’ propaganda – the use of deceit to sap the enemy's morale (for example, by spreading false rumours). Joseph Goebbels was regarded as a master of these arts. His Ministry of Popular Enlightenment and Propaganda was credited with transforming Germany into a single-party Nazi state and fatally weakening the resistance of neighbouring countries before Germany's military conquests – it was thought that German propaganda begat the fifth column. As a result, the British intelligence system paid close attention to the detection of enemy propaganda at home and abroad: it ranked just below sabotage and espionage as a priority for investigation.

Within the British government the task of equalling Dr Goebbels fell to the Ministry of Information. Created on the outbreak of the war, its duties were to channel news to the press, to maintain morale at home and to publicise the Allied cause in the empire and outside. The ministry's first year was not a happy one, as it distinguished itself by its amateurism and muddle. The Prime Minister considered shutting it down after just two months. Its ministerial leaders changed with alarming rapidity, and it was only when Brendan Bracken (an Irishman) took over in July 1941 that it began to operate effectively. One of his first steps was to create the Political Warfare Executive, in conjunction with the Special Operations Executive (SOE), to carry out clandestine propaganda operations. Thereafter the British propaganda system became increasingly ambitious, employing both white and black methods to weaken enemy morale, to foster resistance in the occupied countries and to persuade neutral states to fight against the Axis. Political warfare, or in American parlance ‘psychological warfare’, was one of the key fronts on which the Second World War was fought.