What was the ultimate cause of world war I?
The most important cause of World War I was the hidden alliances. This is the ultimate cause of World War I because if other countries knew about the alliances they most likely wouldn't have attacked a country that had an alliance with another country. Other countries in that alliance would attack the place that declared war on their fellow allies thus getting everyone in the other alliance involved in the fight. Garvrilo Princip, a terrorist from Serbia, killed the Austria-Hungary prince. Then Austria-Hungary got into a fight with Serbia, and they went to war, causing the aligned countries to join the fight causing the World War.