Before I start, I will clear up two things.
Nationalism is not patriotism.
Nationalism is not rooting for your country in the World Cup.
Nationalism, at least in Europe, has been given a bad connotation. Leaders like Francisco Franco, Pol Pot, Ante Pavelić, and Adolf Hitler used nationalism as a tool to manipulate the populus and concentrate power.
What is the difference between nationalism and patriotism?
While the Google definition for “nationalism” is, and I quote, “patriotic feeling, principles, or efforts”, I believe that this is misleading. Patriotism is the love of one’s country. Nationalism is when that love turns into a need to “cleanse” the country. Take Ante Pavelić, for example. He was a Croatian nationalist, not a patriot. What distinguishes Pavelić and your average patriot is that while the average patriot may make anti-Serbian comments, Pavelić used Croatians’ patriotism to kill at least 250,000 Serbs during his rule in WWII.
How do leaders use nationalism?
This time, let’s use Adolf Hitler as an example. After the defeat of the German Empire in WWI, the Treaty of Versailles forced the newly-formed Weimar Republic to pay war reparations, demilitarize the Rhineland, and to shrink their military to 100,000 men. In addition, they had to accept full responsibility for the war, even though a Serbian/Bosnian nationalist had been the cause.
In the parliamentary elections before 1933, Hitler played German anger about the Treaty of Versailles to win an increasing amount of the vote, while he scapegoated the Jews and communists for German defeat.
In 1933, with full Aryan support, Hitler proclaimed himself as the Führer of Germany. In 1938, the Nuremberg Laws, anti-Jewish boycotts, Kristallnacht, and finally, WWII, led to the Holocaust, where Slavs, Roma, disabled people, Poles, Serbs, Freemasons, Slovenes, homosexuals, Jehovah’s Witnesses, and the Jews were executed and deported en masse.
Is nationalism dangerous in the 21st century?
In all these examples, I used notable historical figures to (hopefully) prove why nationalism is detrimental to peace. However, I would like to stress that nationalism is still a threat to the world today, as regimes in China, Russia, Myanmar, Hungary, Romania, and Poland have been using nationalism to build autocratic governments and crack down on free speech.