In a total war, more than in any other type of conflict, victory is dependent on the scale of resources that can be mobilized. Here, we analyze the “blood, sweat, and tears” behind British mobilization for World War II. A war economy is presumably one in which the overriding economic imperative is to achieve the war aims of the nation. A total war economy suggests an even greater intensity, in that all economic resources are mobilized to that end. However, this should not be taken to mean that all able-bodied people in the economy are in the armed forces or the munitions and related industries. An economy that produces guns but no butter will quickly collapse. The armed forces and the munitions workers need to be fed, clothed, housed, transported from home to work, industry needs to be provided with energy, and so on. Nor can the prewar standard of living of the populace be ignored, as they will expect to maintain some minimum level even during the wartime deprivations, and if the state is to be successful it will need to provide incentives. Therefore, the degree of war mobilization - that is, the level of resources directly devoted to the prosecution of the war - that can be associated with a successful total war economy will differ across economies, reflecting their economic capacity.