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What events led to the outbreak of World War I in 1914?
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World War I
A British soldier inside a trench on the Western Front during World War I, 1914–18.
The outbreak of World War I in 1914 was triggered by the assassination of the Austrian Archduke Franz Ferdinand in Sarajevo on June 28, 1914, by Gavrilo Princip, a South Slav nationalist.123
This event set off a rapid diplomatic and military crisis:
- Austro-Hungarian Response: Viewing the assassination as an opportunity to diminish Serbian influence in the Balkans, Austria-Hungary sought to humiliate Serbia. With a promise of support from Germany, they issued an unacceptable ultimatum to Serbia on July 23.14
- Escalation: Despite Serbia’s attempt to negotiate, Austria-Hungary declared war on July 28 and began bombarding Belgrade.12
- Alliance Mobilization: The conflict quickly expanded due to the existing system of alliances. Russia mobilized to support Serbia, leading Germany to declare war on Russia and France.
- Invasion of Belgium: Germany’s strategic plan to defeat France necessitated an invasion of neutral Belgium, which prompted Great Britain to declare war on Germany on August 4.14
By August 1914, these interconnected commitments transformed a regional Balkan dispute into a global conflict between the Central Powers and the Allies.15