This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book describes that nations do not exist without an imaginary realm and that, in the case of Russia, the nation's imaginary is of an imperial nature. It explores nationalism as a doctrine, that is, an attempt to elaborate a set of principles organized into a more or less coherent whole. Western scholarship on Russia has always devoted substantial attention to national identity issues, both to explain Russia's "difference" from the West and as part of a mirror game with Russia's national tradition of debating the so-called Russian Idea. As a political battlefield, nationalism needs not only ideas, thinkers, funders and patrons, but also grassroots-level actors. These are quite marginal and do not constitute a large share of the population.