When we speak of the new architecture of Central and Southeastern Europe after World War I, it is imperative to make the distinction between factual and legal realities. Actually, the entire old order of the region collapsed in the year 1918, when four empires fell (German, Austro-Hungarian, Russian, and Ottoman) and new states were formed, or others were completed according to ethnic and national criteria. The cause of this huge change was, undoubtedly, the peoples' fight for national emancipation, initiated in the 18th century and culminating in the "century of nationalities" and in the 1900s. Obviously, the Treaty of Trianon has its international and national importance which is difficult to estimate and impossible to minimize: it legitimized the just will of the Romanian people and consecrated a valuable legacy at international level.