How can nationalism be both a unifying and dis-unifying force?

Nationalism is a unifying force when the people being united are similar in race, culture, religion, language, etc. It brings common people together into a new definition, basically it makes a bigger group. Nationalism is a dis-unifying force when people who are not similar are united under a single nation.

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have a great day.

1. it was caused by feudalism

2. charlemagne used christianity as a major cornerstone for his rule. cloisters were built all over the empire to act as centers for the (re)population of the vast european wilderness.

3. the europeans feared the next raid every time chetak

i'm not so sure about #6. but i hope i you with the first 3.