War and wealth, or 'blood and treasure', are intimately connected. Thus, war is also an economic activity: it has economic motivations, demands economic resources and has economic consequences. But, over time, as Duncan Weldon explains in this brilliant book, those motivations, resources and consequences have changed. That evolution is not just the result of political and economic developments, but also a leading cause of them. The good news is that the economic gains from major wars have collapsed as the costs have soared. The bad news is even this may not be enough to curb humanity's horrifying propensity for mass conflict.