Final answer:
The assassination of Archduke Franz Ferdinand on June 28, 1914, by Gavrilo Princip, a Serbian nationalist, triggered the outbreak of World War I due to the complex system of alliances in Europe. This event led to a series of demands by Austria-Hungary on Serbia and subsequent declarations of war involving Germany, Russia, France, and Great Britain.
Step-by-step explanation:
The Assassination that Triggered World War I
The assassination of Archduke Franz Ferdinand was the event that led to the start of World War I. On June 28, 1914, in Sarajevo, Gavrilo Princip, a member of the Serbian nationalist group the Black Hand, shot and killed the Archduke and his wife. This act set off a chain reaction throughout Europe due to the complex alliance systems that had been established. Austria-Hungary made severe demands on Serbia, and when Serbia's response was deemed insufficient, Austria-Hungary declared war. This mobilization brought in Germany, Russia, France, and eventually Great Britain due to their respective treaties and alliances.
In the first few months of the war, Europe quickly became divided into two opposing sides with a series of rapid mobilizations and declarations of war. The conflict spread as nations with colonial empires brought their global resources to bear. The historical significance of Franz Ferdinand's assassination lies in its role as a trigger for a war that would engulf the world, due in large part to a powerful mixture of nationalism, imperialism, militarism, and a tangled web of alliances.