There are a number of areas that a study of modern war needs to consider. These are definition, causation, lived experience, and legacy. The Introduction sets out a few questions that this VSI hopes to answer: what is modern war? What causes modern wars to begin, why do people fight them, and why do they end? What has the experience of modern war involved? What have modern wars achieved? There is a discrepancy between what we often assume, think, and claim about modern war, and its historic reality. War remains the most dangerous threat facing modern humanity, and also a key influence shaping politics, economy, and society today.