The Major Empires in Europe prior to WW1 would be the British Empire, France, German Empire, Austria-Hungary Empire, and Russian Empire.
Some Colonial Empires prior to WW1 would be the Belgian, Italian, Spanish, Dutch, Portuguese and Danish.
Nationalism threatens stability of countries, in this case, Europe. With a threat of stability in Europe, unveiled the cause of WW1.
The growing of nationalism was a result of growing knowledge about Democracy, and equality.
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