It would be primarily "The Church and the Crusades" that <span>played a significant role in uniting the kings and people of Europe, since adhering to religious principles back then was the norm for most. </span>
They were treated as if they were gods.
The alliances system meant that a local conflict could easily result into an intimidating global one. The overall cause of World War was the assassination of Archduke Franz Ferdinand. Nationalism was a great cause of World War one because of countries being greedy and not negotiating.
Your welcome I don't know if that helped. But yea.
