On June 28, 1914, Archduke Franz Ferdinand of Austria, the heir to the throne of Austria-Hungary, was assassinated in Sarajevo, the capital of Bosnia-Herzegovina (formally annexed by Austria-Hungary in 1908). The assassin, Gavrilo Princip, was a Bosnian Serb nationalist who was a member of the Black Hand, a secret society dedicated to uniting all South Slavic peoples into a single state.
2. Diplomatic Crisis
The assassination of Archduke Franz Ferdinand triggered a diplomatic crisis between Austria-Hungary and Serbia. Austria-Hungary accused Serbia of being behind the assassination and issued an ultimatum to Serbia, demanding that it take action against the Black Hand and accept Austrian control over its military and foreign policy. Serbia agreed to most of the demands but rejected some, which Austria-Hungary saw as a rejection of its ultimatum.
3. Outbreak of War between Austria-Hungary and Serbia
On July 28, 1914, Austria-Hungary declared war on Serbia, marking the official start of World War I. Russia, as Serbia's main ally, began mobilizing its troops in support of Serbia. Germany, in turn, declared war on Russia on August 1 and on France, Russia's ally, on August 3.
4. Germany's Invasion of Belgium
In order to reach France, German troops invaded Belgium, a neutral country. This violated the Treaty of London, which guaranteed Belgium's neutrality, and brought Great Britain into the war on August 4.
5. Global Spread of the War
World War I quickly spread beyond Europe, with the involvement of colonial empires and other countries around the world. The United States entered the war in 1917, tipping the balance in favor of the Allies (France, Great Britain, Russia, Italy, and the United States).
6. End of the War
World War I ended on November 11, 1918, with the signing of an armistice between the Allies and Germany. The war had lasted for four years and had resulted in the deaths of millions of people. The armistice was followed by the Paris Peace Conference, which resulted in the Treaty of Versailles and the redrawing of the map of Europe.