In the aftermath of the First World War, the victorious powers - more or less liberal democracies - argued that democracy would bring peace to Europe because this was the only effective way for legitimate states, with governments based on the consent of the governed, to be organized. What the victorious statesmen failed to foresee was how much conflict this postwar settlement would provoke, since it was far from clear exactly which people should qualify for the privilege of self-governance. It is well known that these conflicts played out dramatically and violently in eastern and...