This edited collection is the first volume to consider potential new insights afforded by the Russo-Ukrainian War that could be salient for Western defence officials and planners. The contributors reflect on what are likely to be important issues that need to be addressed in order to ensure that Western armed forces are capable of deterring Russia. Closely examining how the war is being fought throughout the battlespace, the chapters avoid falling into the trap of making determinative statements about which developments might be trendsetters or are ‘new’ aspects of modern war.  Rather, and given that this conflict apparently is far from over, the contributors eschew determinism and instead offer open-ended and clear-eyed analysis of what is playing out on the ground. Individual chapters address the following lines of analysis, among others, arising from the war: - Russian thinking on warfare and how it has been misunderstood by many in the West, as well as judging Russian military performance as simply being represented in numerical results. - Manoeuvre, and the growing importance of urban areas in land warfare. - Developments in the delivery of kinetic force (land, air, maritime and cyber) and operational fires. - Longer-term effects of Russia’s rejection of the law of war and its systematic breaches of international legal norms by actively attacking non-military targets (economic, infrastructure, cultural assets), and the implications of this for NATO’s logistic formations and higher-level policy. - Communications—both field signals and strategic narratives.