The assassination of Franz Ferdinand is what started WW1, which was done by Serbian rebels, but the county was Austria-Hungary. The two nations that escalated the conflict was Russia, who supported Serbia, and Germany, who supported Austria.
It's called a "city-state"
The believe that the answer to the question asked above is that leaders responded by looking for more resources to be superior to others, even come to a point invading others for their wealth.
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