Nationalism is an ideology that encompasses national pride, or pride in a culture.
German fascism took roots in an extreme form of nationalism, with Hitler's early annexations of Austria and Czechoslovakia because they had German parts. (WWII Era)
Many countries revolted from the dying Ottoman Empire, such as Bosnia, Serbia, and Greece, on the premise of nationalism: they believed they had an entitlement to a nation representing their culture. (pre-WWI Era)