Divided nations and partitioned countries
The ideal nation-state is a political unit synonymous with a nationality. Such polities abound in textbooks but are rare in the real world. Most nations contain more than one nationality, and nationalities themselves are frequently divided among two or more states. A list of countries, for example, that comprise 90% of all the members of one ethnic group and contain a minority population of 5% or less would be very short indeed. Japan alone among the great powers would appear on the list, and certainly no more than a handful of newly independent countries would qualify. Division, therefore, is a basic and universal problem; and since nations have multiplied in the last generation, so also has division. Divisions and divisiveness have profound political ramifications. The desire for unification or autonomy motivates the participants in a majority of current international conflicts and has led directly to most of the wars fought since 1945.