What do we know and what can we know about what war? Traditionally, international relations has primarily focused its attention on what political ends war serves for states and war’s function in the international system. Feminist IR scholars have, by contrast, paid greater attention to how war shapes and is shaped by people’s everyday lives. They have considered war as an embodied and lived experience and have analysed how gendered norms and expectations create different war roles and insecurities. In an age in which knowledge and expertise and both increasingly questioned and commodified, there are limits to what we can sometimes learn and say about war, however. In this lecture, she draws on insights from some of her recent feminist research on the British military to show how hyper-masculine ideas about the state and security, but also about knowledge and how it is produced, can prevent feminist insights about war from being taken seriously. She argues however that such insights are vital, not only for us to better understand war and what makes it possible, but in order to challenge the prioritisation of knowledge that normalises war over the knowledge that critiques it in international relations.