Nationalism is the feeling of loyalty shared by a group of people united by race, language, and culture. It was born and spreading since 1789 during the French Revolution, and spread by the Napoleon army. To express their loyalty to their nation, people will attempt to fight for independence against foreign rule or unite themselves into one large nation-state. Nationalism therefore was both a uniting force and dividing force; uniting a number of small states into one large nation-state or splitting a large country into smaller ones. This feeling of nationalism therefore directed the people to make many territorial changes on the face of Europe.
First, we should look at changes made by nationalism to the Vienna settlement. Vienna settlement can be seen as a stage that attempts to stop changes from taking place in Europe: it aimed to "turn to clock back", restoring old order, and preserve a "status quo" to maintain balance of power and stability in return for peace. Changes made to it started in 1830, when there was the Belgium War of Independence. The Belgians, forced to unite with Holland in 1815 by the Vienna settlement to create a buffer state to prevent France from further aggression, were serious fed up of the Holland government over them because they were treated like a conquered country and started a revolt. The success of the Belgian revolt was the first important violation of the settlement. Reactionary powers, which suppressed all revolts and uprising previously in Europe, surprisingly helped in the creation of the new Belgian state. Their independence served as great encouragement to those who were still under foreign rule and want their own independence because of nationalist thinking. Belgium Independence was one of the changes made to the map of Europe under the force of nationalism, cutting up the buffer state Kingdom of United Netherlands, creating a new nation, Belgium.
Italian unification carried out during 1858-1870 was another change made to the European map due to nationalism. Italian states were what Metternich described as "geographic expression", no more than a loose collection of states, not a nation. Nationalism increased the desire for these nations to be united into one country. Therefore, the Italians, under the lead of Piedmont-Sardinia, started wars to overthrown foreign rule, changing the original decisions made by the Vienna settlement as to how and who the states should be governed. The Italian unification decreased the power of Austria since some states were ruled by them previously, and gave birth to a new power, Italy. These are changes made by nationalism because the Italian unification is the end product of nationalism.
Almost carried out at the same time was the German unification (1864-1870). Under Prussian, the German states grouped together and form the German Empire. This was an emergence of a new great power, changing the original balance of power. The German Unification was also a product of...