The first event is the Enlightenment. This was a social and philosophical movement that took place in Europe during the 17th and 18th century. The enlightenment is called like that because it used the reason and the scientific knowledge to discuss religious dogmas from the Middle Age.
The second event are the Napoleonic wars. These wars happened during the early 19th century while Napoleon I ruled over the French Republic. After all these conflicts the idea of a Republic spread through Europe and more monarchies were not seen as the only option for a country.
The third event is the congress of Vienna. Shortly after Napoleon’s defeat, during the Napoleonic wars, on 1814. Representatives from all the countries in Europe gathered and established territorial boundaries and peace agreements to avoid future wars.
The fourth event is the German Unification. Before the German Unification there was 39 German States that on 1871 merged in order to create the German Empire. The German Empire gathered a lot of power and lasted until the first World War.