On the eve of the First World War, the film industry was flourishing in Europe and the United States. A widespread and warmly appreciated spectacle in the popular classes as well as among social elites, cinema contributed powerfully to the extension of mass culture, media and information. The outstanding example of this dazzling development was perhaps the success of Pathé, which was the world’s leading film company until around 1910. In 1918, as business gradually dwindled, the hegemony of the French cinematographic industry disappeared almost entirely, to the benefit of American productions. At the same moment, cinema emerged as a separate art form − an essential part of the new times, the modern age. As Louis Delluc wrote in 1919, ‘an art was born during the war… The time will come when cinema, an entirely new art, will impose its full power.’ The aim of this chapter is to retrace cinematographic activity and its evolution during the war, describing the functioning of what is generally known as ‘propaganda’ through the cinema. We focus on the strategies and stakes established within the framework of ‘cultural mobilisation’, and offer a critical reading of certain major and recurrent themes on the screen and their relation to the audience in both news and documentaries on the war and in patriotic fictional film. We use various sources for the conditions of production and distribution, and the place of films in societies at war.