What condition are necessary to create nationalism and a nation?

For starters, a factor needed to create Nationalism must be Ethnic unity and pride. From there, if the ethnicity's people are assimilated, they will seek to create a homeland where there kin will live together as one. If the ethnicity live in separate states, like the various German states that existed in the regions before 1867, they will seek to unify those states into a large nation. This is the usual goal of Nationalists seeking unity. However, some extreme Nationalists may target minorities or claim ethnic superiority as their secondary goals.

For people to express nationalism it is first necessary for them to identify themselves as belonging to a nation, that is, a large group of people who have something in common. The rise of centralized monarchies, which placed people under one rule and eliminated feudalism, made this possible. The realization that they might possess a common history, religion, language, or race also aided people in forming a national identity. When both a common identity and a formal authority structure over a large territory (i. e., the state) exist, then nationalism becomes possible.