How can we best explain the high war-propensity of certain states, especially if it persists over long periods of time, beyond the tenure of specific leaders? A related question is why is the danger of war concentrated in some specific locales such as China-Taiwan, Korea (and earlier also in Vietnam), Kashmir, the border area between Afghanistan and Pakistan, Turkey-Greece-Cyprus, Israel-Palestine-Lebanon-Syria, Iran-Bahrain/Iraq-Kuwait, the Balkans, and the Caucususwhile the danger of war almost doesn'te x i s ti no t h e rp l a c e s ?I si t because of factors related to the global or regional balance of capabilities, the type of domestic regimes, or are there perhaps alternative causal factors? I argue that the key for explaining variations in the war-propensity of states is their state-to-nation balance. This balance is composed of three major components: (1) The extent of success in state building, that is, state capacity or the level of stateness; (2) The level of internal national congruence; (3) The extent of external national congruence. Two key factorsdemography and historyinfluence the likelihood that the national incongruence will be translated to nationalist challenges to the status quo.Some of the key manifestations of the nationalist dissatisfaction with the status quo include: "illegitimate states," pan-national movements, irredentist-revisionist states, failed states, and "illegitimate nations." Internal incongruence and state weakness lead to challenges of incoherence manifested by "nations without states," failed states, "states without nations," and stateless refugees. External incongruence and state strength lead to revisionist challenges manifested by pan-national movements of unification or irredentist claims to territories held by other states on the grounds of national affiliation of the population or national-historic rights on the territory.More specifically, variations in the extent of stateness and national congruence determine the level and the type of large-scale violence by producing different categories of states with regard to their war-proneness. 73 terms of use, available at https:/www.cambridge.org/core/terms. https://doi.