Nationalism

Nationalism is an ideology in which people align themselves with a particular nation-state, usually the one in which they reside or were born in.

In Europe, the ideas of nationalism and liberalism led to the end of feudalism and the rise of strong central governments, dramatically improving quality of life through early modern age.

However in the 20th century, nationalism led to two disastrous world wars.

Communists dismiss nationalism as a tool that the bourgeosie use to keep workers divided and confused (similar to how they use religion).