Answer: Nationalism refers to the belief that a particular nation or ethnic group is superior to others, and that its culture, history, and values should be promoted and protected. During WW1, Nationalism played a significant role in the outbreak of the war, as many countries were motivated by the desire to assert their national pride and power. Nationalistic sentiments were used to rally citizens to support their country's war efforts and to justify aggression against other countries. Nationalism also led to the emergence of several new countries after the war through the dissolution of empires and the creation of nation-states based on ethnic or linguistic lines.