Which event lit a “powder keg” in europe and led to the start of world war i? russia joined a war between austria-hungary and serbia.  austria-hungary declared war on serbia due to ethnic uprising. archduke franz ferdinand was assassinated by a serbian nationalist. archduke franz ferdinand stopped a revolt of serbian nationalists.

The event that lit a "powder keg" in Europe and led to the start of World War I was the assassination of Archduke Franz Ferdinand by a Serbian nationalist. This assassination put in motion a number of pre-existent causes such as nationalism, imperialism, and a net of previous alliances between the major powers involved.

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