Nationalism was nothing new to Europe in 1919. The notion of the “nation” as an ethnic political community, which competed against other ethnic political communities (Germans against the French, Serbs against Austrians, etc.) was one of the main causes of the war in 1914. Nations competed with each other in every possible way in the prewar world. Some of these competitions were mostly innocent, like the establishment of the modern Olympic Games in 1896. Others were destructive, like the race for colonial possessions in Africa and political and/or economic domination throughout Asia and South America. What was new after the war was the complexity of nationalistic issues in Europe after the fall of the old empires. Such complexity led to dozens of struggles over the precise borders of the new nation-states. The results of these border struggles, most of which played out in 1919 and during the first years of the 1920s, were just the beginning of the story and set the stage for more enduring tensions and conflicts. The division of empires into nations left millions of people on the “wrong” side of ethnic divides. Tens of thousands of Hungarians, for example, found themselves not governed from Budapest but from Prague. Hundreds of thousands of Germans found themselves in Poland and Czechoslovakia. Austrians became Italians (many changed or Italianized their names). Hungarians became Romanians. Czechs and Lithuanians became Poles. Slovenes became Austrians. Germans became Danes, and so on. Building nations included making difficult and often bitter decisions of inclusion and exclusion; minorities who ended up within another ethnolinguistic nation often faced discrimination and hostility. Nations that lost territory longed for it back. Important areas like coalmines, ports, and industrial centers were taken from one country and given to anther, furthering economic and political stress.

The most complicated cases of creating nations out of empires in the aftermath of WWI were found in three principle places: 1) the creation of the state of the South Slavs, Yugoslavia, out of Croats, Serbs, Slovenes, Bosnians, Montenegrins, and other minorities, 2) the founding of new Central European nations in Poland, Czechoslovakia, Hungary, Romania, and Austria, and 3) the formation of a democratic Germany.