The break-up of empires was the most profound geo-political phenomenon of the twentieth century. In 1900, except in the Western Hemisphere, most of the world's people lived in polities which readily described themselves as empires. These polities were territorially vast, or at least far-flung, and each of them ruled a multitude of peoples who differed enormously in the usual markers of ethnicity such as language, religion, and culture. Over the course of a century, however, most of these empires disappeared. The territorial empires of the Habsburgs and the Ottomans fell apart in the aftermath of the First World War, the colonial empires of the Germans, British, Americans, Dutch, French, Belgians, Spanish, and Portuguese gave way to a combination of nationalist and international pressures, the wartime conquests of Germany, Japan, and Italy came to nothing, and finally the Soviet Union fragmented into a multitude of new, independent states at the end of the Cold War. Smaller polities such as Yugoslavia and Ethiopia fractured into still smaller ones.