“Comparative history,” according to two of its main academic proponents, Heinz-Gerhard Haupt and Jürgen Kocka, “is analytically ambitious and empirically demanding” (Comparative and Transnational History: Central European Approaches and New Perspectives [2009]). One might add “linguistically challenging” to the list of difficulties. Anand Toprani has overcome all of these challenges and produced a rich and detailed comparative historical study of Germany's and Britain's quest for energy independence during the first half of the twentieth century. Based on extensive archival material and primary sources in both English and German, his ambitious analysis is driven by a more conceptual interest in the interconnections between energy and geopolitics. Comparing Germany's and Britain's national experiences between 1914 and 1945, he observes a more general historical pattern and correlates the lack of access to oil with great power decline.

Devoting four chapters each to his two case studies, Toprani discusses in meticulous detail national attempts to establish energy independence, or what might be labeled more precisely as oil independence. Before 1914, industrialized Britain and Germany may have achieved energy independence with regard to coal, but World War I had shown that any future power struggles would be decided by having access to oil, which was scarce in both countries. Although they may have shared the belief in the strategic necessity to supply a larger (existing or future) empire, Britain and Germany differed significantly in their geopolitical position, one being a naval and the other a continental power. Nevertheless, Toprani argues, it was the common plight of insufficient national oil supplies, which “hasten[ed] their demise as great powers” (1) in the twentieth century and helped explain the emergence of the two superpowers, the United States and the Soviet Union, both oil-rich countries, during the “Age of Oil.”

Toprani's separate empirical discussions of Britain (chapters 1–4) and Germany (chapters 5–8) may not always contain new insights for energy historians of both countries, but they provide more historical detail and evidence of the development, change, and contestation of the strategic thinking behind achieving oil independence. Using a wide range of government and some industry sources for both his case studies, Toprani's analysis is best when reconstructing how various government departments and state actors proposed their—sometimes conflicting—strategies to achieve oil independence.

In the British case, most of these discussions focused on the Middle East (Iran and Iraq), even more so after British oil interests were nationalized in Mexico in 1938 and US companies edged out British competitors in Venezuela. Here, Toprani makes an excellent analytical point about the surprising lack of understanding by British planners in World War II of the strategic importance of moving oil. Middle Eastern oil could only be an asset for Britain as long as it could be safely transported across the Mediterranean, but once Italy entered the war, Britain was forced to purchase oil elsewhere in dollars and thus lose its oil independence.

In contrast, Germany did not exclusively focus its attention on gaining control of oil reserves, mainly in Romania, the Caucasus, and the Middle East. It also hoped to overcome its oil dependence through producing synthetic fuels. The magnitude of this endeavor as well as the instrumental role of IG Farben have been studied before, but Toprani manages to embed this story into a larger narrative of energy independence planning. Among his strongest contributions are his discussions of German-Romanian oil diplomacy and the creation and workings of the Kontinentale Öl AG (Continental Oil Company) for the German case study as well as the inclusion of the heretofore understudied Oil Board of the Committee of Imperial Defence for the British case.

Another strength of Toprani's analysis lies in the minute reconstruction of oil projections and strategies throughout the time period under examination and the interdepartmental struggles over who would determine such strategies. At the same time, it is this richness of historical detail that sometimes overwhelms the reader and clouds the larger trends and interpretations. In addition, the sequential structure of the comparison makes it difficult to systematically consider the similarities and differences of the two case studies. Considering that most of the oil independence strategies were guided by wartime planning, it would have been interesting to learn how a democratic state (Britain) differed from an authoritarian regime (Germany). Equally useful would have been a discussion of why both governments decided to create oil companies with considerable state participation, and what role stockpiling and oil storage played in strategic thinking on oil independence. Finally, a more focused comparison of the relationship between industry and the state would have added significantly to the book's understanding of oil independence. Although it is reasonable that for this time period and because of Toprani's interest in strategic thinking, the focus would be on oil as a strategic good, oil continued to operate also as a commercial good. Thus, any discussion of oil independence would benefit from an analysis of economic actors as well as consumers who were affected by rationing.

Despite these lost opportunities to uncover further historical patterns through comparison, Toprani's study is a welcome addition to the literature on oil and war, one that is empirically rich and proposes an important historical argument. It is also much more nuanced in its understanding of what is actually meant by oil and oil independence. Toprani succeeds in differentiating between the various types of petroleum products and their usefulness in warfare. He also addresses the much more complex and intricate nature of having access to oil. As the aforementioned example of Britain has shown, it is not enough to focus on the mere existence of oil resources or upstream activities (drilling and production) to understand whether countries will have access to oil or not. Equally important are midstream (transportation) and downstream (refining) sectors that ensure and sustain the flow of oil. Without a sufficient number of tankers or free passage across the Mediterranean, Britain's control of oil production in Iran could not ensure its oil independence. Historical insights like these are an important corrective to more generalized arguments about oil and war. Unfortunately, as critics of comparative history have cautioned, generalizations obtained from empirically detailed but limited (two countries) comparisons can go only so far.