The event that immediately triggered the start of World War I was the assassination of Archduke Franz Ferdinand of Austria, the heir to the throne of Austria-Hungary, on June 28, 1914, in Sarajevo (present-day capital of Bosnia and Herzegovina), when he was shot dead by a Serbian nationalist named Gavrilo Princip.
Here is a sequence of events leading up to the assassination:
1. Austro-Hungarian expansion in the Balkans: Austria-Hungary, a major power in Central Europe, had long sought to expand its influence in the Balkans, an area of diverse ethnic groups and conflicting territorial claims.
2. Serbian nationalism: The Balkans was also a region of growing nationalism, particularly among Serbs, who desired to unite all Serbian-inhabited lands into a single state. This ambition directly conflicted with Austria-Hungary's expansionist goals.
3. Black Hand: The Black Hand, a secret society within the Serbian military, was dedicated to achieving Serbian unification, even through violent means. They organized several plots to assassinate prominent Austrian figures.
4. Visit of Archduke Franz Ferdinand: In June 1914, Archduke Franz Ferdinand visited Sarajevo, the capital of Bosnia and Herzegovina, which was annexed by Austria-Hungary in 1908. The timing and location of the visit were seen as a provocation by many Serbian nationalists.
5. Assassination: On June 28, 1914, during the archduke's motorcade procession in Sarajevo, Gavrilo Princip, a Bosnian Serb and a member of the Black Hand, fired two gunshots, fatally striking Franz Ferdinand and his wife, Sophie, Duchess of Hohenberg. The assassination ignited widespread outrage and outrage.
6. Diplomatic Fallout: The assassination triggered diplomatic tensions between Austria-Hungary and Serbia. Austria-Hungary, seeing the assassination as a consequence of Serbian nationalism and support from the Serbian government, issued a series of demands (the July Ultimatum) that the Serbian government found unacceptable.
7. Failure of Diplomacy: Diplomatic efforts to resolve the crisis failed, and on July 28, 1914, Austria-Hungary declared war on Serbia. This declaration marked the beginning of World War I as the system of alliances and rivalries between European powers led to a chain reaction mobilizations and declarations of war.