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The immediate cause of World War I that made the aforementioned items come into play (alliances, imperialism, militarism, and nationalism) was the assassination of Archduke Franz Ferdinand of Austria-Hungary.
It was justified through the Mandate of heaven. Basically. It was thought that only one legitimate ruler could be the ruler of china. And whoever that one ruler was, he was blessed with godlike powers.
Colonialism hindered a developing country's level of development. ... There was investment in colonies, but this was focused on things that would help the trade between the countries. Borders of some colonial countries were set without attention to tribal and cultural differences, causing tensions and instability.
