During the First World War the Principle of Nationalities (each nation to have its national state), a prinsiple supported also by the USA, was crystallized and accomplished. On the ruins of the Austro-Hungarian Empire, Czechoslovakia proclaimed itself independent, its borders being set up by the treaties system from Versailles. During the years of the First Republic, Czechoslovakia has imposed itself as a state with a stable economic development, with an authentic multiparty democracy. At the same time, being supported by nazi Germany, the ethnic Germans from the Sudet region of Czechoslovakia ultimately requested the accession of this region to Germany. Otherwise, A. Hitler threatened to start a war in support of the Germans from Sudet. The Great Powers got involved. Hitler’s claims were met at the Munchen Conference. This fact led to the dissapearance of Czechoslovakia from Europe’s political arena.