What condition are necessary to create nationalism and a nation?

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.