Political formations in the Balkans in the wake of the First World War, though tangled and complex, appeared relatively simple in comparison to Central Europe. Here, the situation was the opposite: fragmentation instead of unification. Yugoslavia had managed to come together basically on its own without the steering of peacemakers in Paris. The new Central European countries, on the other hand, required the blessing of the great powers in Paris for their survival. Two countries stand out as representative of the nationalist, ethnic politics that defined the era: the union of Czechs and Slovaks into the nation of Czechoslovakia, and the formation of Poland after 120 years of partition and national nonexistence.

Czechoslovakia formed around industrialized Bohemia and the more rural Moravian and Slovak lands. These regions had long been part of Austria-Hungary. No clear boundaries existed between the Czech and Slovak lands and the domains of surrounding peoples, including Germans, Poles, Hungarians, Austrians, and Ukrainians. The political reality of the post-WWI world allowed the Czech government, which had declared its independence in 1917, to push out its frontiers at the expense of the surrounding countries, all of whom were either as yet unformed (Poland, Ukraine) or were facing military defeat and surrender (Germany, Austria, Hungary). Again, as with Yugoslavia, border disputes between Czechs and neighbors erupted immediately. In the end, hundreds of thousands of Hungarians, Germans, and Ukrainians fell under Czechoslovak rule. Many Germans, who were content to live under Austrian governance, did not feel comfortable with rule from Prague. The result of this struggle for border regions between countries in Central Europe (and these border regions tended to be rich in industrial, commercial, or natural resources) was increasing hostility between neighbors. Germans felt like the government in Prague had stripped Germans in the Czech Sudetenland of rights. Hungary saw hundreds of thousands of ethnic Hungarians living on the other side of the Czechoslovak border. The situation was precarious. Later, Axis powers (Italy and Germany) would exploit these regional hostilities to draw allies to their side in WWII. It is no surprise that Hungarians, Bulgarians, Austrians, and Croats (and to some extend Slovaks), the losers in the border and political disputes between 1919-1939, would become the aggressors when Hitler destroyed the European balance of power in 1939. Nationalism was a driving force behind nations’ determination to gain what they considered “rightfully” theirs.

The case of Poland was especially challenging and fraught with danger. In the 1790s, Poland, once a Central European powerhouse, was partitioned and erased from the map by the empires of Austria-Hungary (the Habsburg Empire), Prussia, and the Russian Empire. The partition of Poland left tens of millions of Poles without a state and subject to foreign occupation and rule; it also oriented the resources of the country abroad. Poles, like Czechs and Slovaks, Serbs and Croats, felt the weight of foreign occupation and an unequal society. The end of WWI presented Poland with a golden opportunity. Throughout the previous decades, a Polish nationalist movement had been gaining strength. Without the simultaneous collapse of the three empires, however, few could see a real path to nationhood for the outgunned Poles. WWI, as we know, caused the three great Central European empires to crash. Polish troops, under the leadership of General Pilsudski, moved quickly to fill the void. By 1919, Poland had reclaimed its nationhood and was trying to do what all nations after the war were attempting: to push out its boundaries as far as possible. This meant that Poland would take territory from Lithuania (it managed to take a large chunk, including the city of Vilna/Vilnius). It meant that Poland would fight for lands in the Ukraine, which included the oil-rich area around the city of Lemberg (Lviv in today's Ukraine). It meant that territory to the south would be contested with Czechoslovakia and that to the north Poland would demand (and receive) access to the Baltic Sea from Germany, including the heavily Germanized city of Danzig/Gdansk (90% German in 1918). What’s more, this so-called Polish Corridor (Poland’s access to the Baltic Sea) meant that Poland cut off Germany’s area of East Prussia from contiguous Germany, a source of public outcry among Germans. In the end, Poland incorporated into itself millions of Germans, Ukrainians, Lithuanians, and Jews. Like Yugoslavia and Czechoslovakia, these border disputes entrenched animosities between neighbors and heightened tensions throughout Central Europe.

These tensions were based on three principle things. First, each nation (there were a lot more now!) wanted as much territory as possible. Second, each nation wanted as many people as possible, foremost all of the people claiming or belonging to its primary ethnicity. Third, each country wanted to maximize its access to raw materials in order to support continued industrialization. All of these nations knew that economic and military power depended on ready access to coal (and increasingly to oil), iron, grain, timber, and other basic commodities. Most territorial conflicts between nations contained an element of resource competition; and nothing symbolized this more clearly then France’s claims on the German coal mines in the coal-rich territory of the Saar.