What event triggered the beginning of World War I?

The assassination of Archduke Franz Ferdinand is recognized as the pivotal event that triggered the beginning of World War I. On June 28, 1914, Ferdinand, the heir to the Austro-Hungarian throne, was shot by Gavrilo Princip, a member of a nationalist group seeking independence for Slavic peoples from Austro-Hungarian rule. This assassination set off a chain reaction of alliances and treaties that plunged Europe into conflict.

Ferdinand’s death led Austria-Hungary to issue an ultimatum to Serbia, where nationalist sentiments were strong. The situation escalated when Serbia’s response was deemed insufficient, leading Austria-Hungary to declare war on Serbia. This declaration activated a web of alliances between major powers, ultimately resulting in a global war.

The other events mentioned, such as the sinking of the Lusitania, signing of the Treaty of Versailles, and the invasion of Poland, played significant roles in different contexts or later conflicts but did not initiate the start of World War I itself. The Lusitania sinking occurred in 1915 and influenced U.S. opinion on joining the war, the Treaty of Versailles was signed at the end of World War I in 1919, and the invasion of Poland marked the