Nationalism refers to the loyalty and devotion to one's nation or country, often prioritized over loyalty to other groups or individual interests. Before the emergence of nation-states, people's primary loyalty was usually towards their local community or religious group. However, the rise of large, centralized states diminished local authority, and the increasing secularization of society weakened loyalty to religious groups. Despite this, shared religion, along with common ethnicity, political heritage, and history, remains a key factor in uniting people in nationalist movements.
Early nationalist movements in Europe during the 18th and early 19th centuries were liberal and internationalist in nature. However, over time, they became more conservative and focused on local interests. Nationalism is often cited as a significant factor contributing to World War I, World War II, and many other modern wars. In the 20th century, nationalist movements in Africa and Asia frequently emerged in response to colonialism. Following the fall of the Soviet Union, strong nationalist sentiments in Eastern Europe and the former Soviet republics led to ethnic conflicts, such as those in the territories of the former Yugoslavia.