Nationalism is one of the causes of World War I.  Nationalism is what made people become proud of their country. It also makes them support and fight for their country. Including imperialism and militarism, countries started to increase their armies power. Countries like Italy, Germany, Russia, and France became great powers. Nationalism encourage countries to be independent. Other countries that weren’t a great power like Serbia wanted to be independent because of Nationalism. They wanted to form their own country and be separate.