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Revisiting Insularity and Expansion: A Theory Note

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What is the relationship between insularity—a state’s separation from other states via large bodies of water—and expansion? The received wisdom, prominent in (though not exclusive to) realist theories, holds that insularity constrains expansion by making conquest difficult. We contend, by contrast, that this received wisdom faces important limits. Focusing on U.S. expansion via means short of conquest, we interrogate the underlying theoretical logics to demonstrate that insular powers enjoy two distinct advantages when it comes to expansion. First, insularity translates into a “freedom to roam”: because insular powers are less threatened at home, they can project more power and influence abroad. Second, insularity “sterilizes” power, which explains why insular powers are seen as attractive security providers and why we do not see more counterbalancing against them. On net, existing scholarship is correct to argue that insularity impedes conquest between great powers. Still, it has missed the ways that insularity abets expansion via spheres of influence abroad. One consequence is an under-appreciation for the role of geography writ large and insularity in particular in shaping contemporary great power behavior.

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