|The region that would become Germany was populated by Germanic tribes well before the coming of the Roman empire to the region. Though they largely resisted Rome, some served in the Roman legions. Germanic barbarian invasions did, however, contribute to the ultimate fall of Rome. Charlemagne united most of the region, but it was a fragile unity and during the time of the Holy Roman Empire, there were several hundred individual political bodies in the territory of the Germanic peoples. The political fragmentation grew only more complex in the 16th century with the Protestant Reformation, which had its roots in Germany. The Congress of Vienna agreed to the creation of a German League composed of 39 states. Of these were 5 kingdoms including Prussia which went on to conquer its neighboring states and declare a German empire under its chancellor, Otto von Bismarck. Germany became an industrial powerhouse in the late 19th century, with a modest colonial empire and serious military aspirations. Kaiser Wilhelm II ruled the german empire at its height just prior to the First World War. Germany's defeat in that war was so complete, however, and the terms of its surrender so humiliating that the seeds were sown for an even greater catastrophe, the Second World War. The Weimar Republic, set up after the war, was never able to truly overcome the economic problems, labor unrest, and political fragmentation of the post-war period. Hitler became chancellor in 1933, functionally ending the Weimar Republic and ushering in one of the darkest chapters in world history. After annexing Austria and Czechoslovakia, Hitler pounced on Poland in 1939, going on to steamroll over most of Europe. In the wake of the Nazi war machine, millions were killed, including most of the Jewish population of Europe. Germany itself was devastated and with the end of the war, it virtually ceased to exist as a political entity. Divided between the Allies, into zones of occupation, Germany began to epitomize the deepening Cold War between the West and the Soviet Union. Two Germanies eventually were created: a West Germany, shaped on the parliamentary republic model and led by Konrad Adenauer and an East Germany, repressive, single-party, and deeply tied to the Soviets. To keep the population of East Germany from escaping, the government constructed the formidable Berlin Wall in 1960, which was not dismantled until 1989 as the inevitable fall of communism became increasingly clear. The reunification of Germany took place in 1990 and though the initial euphoria has dimmed, Germany continues to work on solving its problems (particularly the economic ones associated with having had to absorb a stagnant East Germany into the booming West).