Final answer:
World War I began with a series of events including ultimatums, assassinations, and declarations of war before spreading across Europe.
Explanation:
Chronological order of events at the beginning of World War I:
- Austria-Hungary delivered an ultimatum to Serbia, which reached out to Russia for help.
- Archduke Franz Ferdinand was assassinated.
- Austria-Hungary gained full support from its ally Germany for the war with Serbia.
- Austria-Hungary declared war on Serbia.
- Germany declared war on Russia.
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