Summary My book project is titled "Martial Theory: How French Thought Went to War." It examines the militarisation of French thought in the second half of the 20th century. In the 1970s and 1980s in particular, leading thinkers adopted war as a frame for theorizing such distinct phenomena as international relations, historiography, power structures in civil society, science, and the nature of thought itself. They all returned to older Prussian military concepts and ideas that had emerged against the background of modern mass warfare. The book examines how the French theorists latched on to these ideas, but transformed and retooled them into a martial theory in its own right. In other words, it examines how war became a way of thinking, a mode of theorizing.