Given the centrality of Hague Law to the lawful prosecution of warfare, the relative paucity of dedicated works is surprising. The general formulation of Hague Law rules is largely uncontroversial, but this clarity stands in stark contrast to their interpretation and practical application. How precisely, for instance, the fundamental rules of distinction and proportionality in attack are to dictate and constrain the planning and practice of warfare continues to be highly uncertain. This important new publication fills the gap in the literature. Offering a comprehensive assessment of Hague Law, it explores questions of definitions and accountability and navigates the substantive rules and their application to different types of warfare.