Nationalism stems from internal or external forces pressuring unity and cohesion among individuals in societies, and produces wide-ranging effects, from a distinct but peaceful national identity to mobilization for warfare, racism and hostility towards disliked groups. Nationalism stems from two primary concepts. Experts embracing the modernist theory assert that nationalism stems from a political catalyst, uniting people based on social norms and national borders, while those supporting the primordial theory assert that people naturally identify with those similar to themselves in physical appearance, social customs and beliefs, causing the formation of bonds among similar individuals.
Regardless of whether caused by political and external motives or biological drive, nationalism produces various effects, some positive and some negative. In the 1700s, French citizens employed nationalism as a catalyst for change. They mobilized as a unified group, protesting dismal living and economic conditions experienced under the reign of Louis XVI and Marie Antoinette. Nationalism also mobilized American citizens during World War I and World War II, demonstrating support for military action overseas. Similarly, the terrorist attacks of September 11, 2001 brought a resurgence of American nationalism. Sometimes, such as the rise of Hitler and Nazi Germany, nationalism proves destructive. Germany, believing itself superior, engaged in warfare with other nations and launched campaigns against dissimilar ethnic groups, ultimately seeking their demise.