The German nationalism that was created leading up to world war two was the main reason for many people joining Adolf Hitler's "Nazi Party." Hitler also manipulated the German people into following his ideological beliefs through the use of profound propaganda. At the time Germany was in a tough economic situation and many people were looking for a way out of the economical pit that the country was in. The Nazi Party began using its "fictitious nationalism " to blame the Jewish people for the economic problems that the country was experiencing. Claiming that the Jews directed an international conspiracy of finance capitalism and Marxist Socialism against German culture, the German people, and German race. These nationalistic views resulted in the expulsion of "inferior " races. In the spring of 1941 the killing of Jewish people began and opening of the first concentration camp, the Auschwitz and which was eventually supplemented by a much larger camp in Birkenau called the Auschwitz II. One of the greatest wars the world has ever seen resulted in the death of over sixty million people and eight-five million if you include war famine and war related diseases. That's approximately 2.5% of the world's population at the time. This was all a result of Adolf Hitler's political and extreme ethnocentric nationalistic agenda. This is one of history's primary examples of how nationalism almost always results in a certain group of people becoming vilified, or in this case slaughtered without mercy.
Even before the popular example of World War two, nationalism proved detrimental. In 1914 five Serbian and one Bosnian nationalists assassinated Archduke Franz Ferdinand of Austria, which undoubtedly was one of the main events during that time that kicked off world war one. World war one saw the slaughter of millions, the reshaping of empires and colonial territories, deadly innovations in warfare, and an unstable peace that eventually ushered in the even more destructive World War Two.