When William Came by Saki (H. H. Munro) is a unique novel in the genre of invasion literature. Starting after a fictional war between Britain and Germany, it depicts no scenes of invasion. Recently, there have been studies from the perspective of how Munro and other authors in the genre viewed Germany and Britain. Some studies also refer to Munro’s deliberate lack of depiction of the war. However, it seems that no studies have looked into the reasons why the war is not depicted. This paper argues that the story is not about showing British military unpreparedness but about how psychological weapons work. It could even be said that depictions of war would distract from the focus on propaganda and its effect on people. Considering this work as being about a British and German propaganda war opens up a new perspective that is different from previous studies. When William Came is a work that points out Britain’s unpreparedness for psychological war by imagining and detailing possible propaganda strategies. It has been said that the novel’s ending is unsatisfactory, as it only ends up showing the potential for youth resistance. However, if it is understood that this novel, from beginning to end, is about a propaganda battle, a war that is fought under the surface, then the final chapter can also be understood as a thrilling one.