The negotiators were all very polite, they wore top hats, Lloyd George, Clemenceau and the rest of them. They decreed that Germany would pay enormous reparations and that life would be practically impossible for a while, which materially helped Hitler later on. The Austrian-Hungarian empire disintegrated and the peace treaty created Yugoslavia, which had never been a coherent country and today proves that it wasn't ready to be one, except under Communist leadership, and therefore a restricted one. Croatia and Slovenia were parts of the Austrian Empire, Serbia was always independent, and so was Montenegro, defiantly independent for an awful long time, and is a fascinating country. Bosnia used to be occupied by the Ottoman Empire and which was therefore largely Muslim.
Differences occur elsewhere.
Russia and Poland have always been antagonistic, because one was always Catholic, and more Catholic than most Catholics because of their proximity to Orthodoxy. They use a different alphabet, but their language is recognisable to one another. But one is Orthodox with a Cyrillic alphabet, and the other has a Roman alphabet and is Catholic. The incompatibility, is really old. Old perfumes from the past still drift across and influence people.