The extent to which the German concept of blitzkrieg was influenced by British ideas on mechanized warfare is a subject of much controversy. Less explored is the influence of such British theories on Soviet doctrine, which adopted a similar idea until abandoning it shortly before World War II. In this excellent, sophisticated study, Habeck shows the influences working on both Germany and the Soviet Union as they sought to make sense of World War I and the Spanish civil war. Her account covers a range of factors, including the impact of industrialization, the role of forceful individuals, and broader views about the conduct of war. She concludes that all these elements interacted to produce particular military concepts until the actual experience of fighting a war forced both armies to think again. A related observation, challenging for academic theorists, applies to other cases as well: militaries take whatever lessons they want from combat and can justify any tactical or operational change that they wish.