Russia’s aggression against Ukraine has led to an increased interest in knowledge about warfare. The public debate about this war has become a test for the expertise skills of numerous scholars and government analysts. Within a few months, a new epistemic community emerged, which began to create a security discourse around the problems of the Russian-Ukrainian war. The article tries to explain the key terms used in this discourse and to indicate what classical texts in the field of international relations say about the causes and course of the Russian-Ukrainian war. In order to compare theory with practice, the author analysed several hundred expert publications on the war and conducted a total of several dozen interviews and surveys in 2022 in the Polish expert community. This text is therefore based on both a theoretical analysis and an insight into the reasoning of the epistemic community of experts educated in the field of security studies.