Power Vacuums in Great Power Politics: The Consequences of Retrenchment and Collapse

In this dissertation, I investigate how great powers respond to the emergence of power vacuums, which I conceptualize as instances of international authority collapse such as occur during great power retrenchment and collapse. I am primarily interested in answering the following questions: why do great powers seek to assert authority in some power vacuums but not others? And what determines their choice of strategy when they decide to compete for it? Specifically, when do they launch military interventions to establish direct rule over a power vacuum, and when do they merely seek to establish indirect rule by providing military and economic aid to favored political actors on the ground?

My central argument is that great powers compete for authority over power vacuums when they fear an adversary could assert control over the respective space and thus shift the geopolitical balance of power, which is a function of material resources and geography, in its favor. Which strategy a great power employs towards a power vacuum in which it has a strategic interest primarily depends on the interaction of two factors: first, whether a genuinely vital interest or only an important interest is at stake; and second, whether the collapse of international authority coincides with the collapse of national authority structures in the respective political space.

To test my argument, I employ a two-pronged qualitative testing strategy. First, in order to show that my theory offers insightful explanations of consequential historical cases, I provide three in-depth case study chapters assessing cases which are clear instances of the phenomenon under investigation, show the proposed mechanisms at work, and are grounded in an extensive study of the empirical record: the collapse of Nazi Germany’s empire in Europe, the collapse of the Japanese empire in East Asia, and the collapse of the British empire in the Middle East. To corroborate the external validity of my findings, I then conduct a large-N qualitative analysis (LNQA), i.e., qualitative assessments of every single case, of power vacuums emerging in the time period of 1945–1989.

Beyond providing the conceptual, theoretical, and empirical foundation necessary for more informed academic and policy debates concerning power vacuums, this study makes several additional contributions to the IR literature. First, it helps enhance our understanding of both the dawn and dusk of the unipolar era, two moments of momentous importance for the nature and conduct of international politics. Second it expands our understanding of the causal role of great power war, which to this day is usually considered merely as an explanandum, not an explanans. Finally, it advances the theoretical debate surrounding the nature and role of hierarchy and authority in international politics.