- Heir to the Austro-Hungarian Throne: Archduke Franz Ferdinand was the heir to the throne of the Austro-Hungarian Empire. His assassination on June 28, 1914, in Sarajevo, the provincial capital of Bosnia-Herzegovina (formally annexed by Austria-Hungary in 1908), was a significant provocation.
- Nationalist Sentiment in Bosnia-Herzegovina: Bosnia-Herzegovina was a region with a complex ethnic and religious composition, including Slavic, Serbian, and Muslim populations. Many Serbs desired unification with Serbia, while the Austro-Hungarian Empire sought to maintain control. The assassination of Archduke Franz Ferdinand exacerbated these tensions.
- Serbian Involvement: The assassin, Gavrilo Princip, was a Bosnian Serb nationalist and member of the Black Hand, a Serbian nationalist secret society. This connection led Austria-Hungary to believe that the Serbian government was involved in the plot and issued an ultimatum to Serbia, demanding they punish those responsible and take action to prevent such acts in the future.
- Diplomatic Crisis: Serbia agreed to most of Austria-Hungary's demands, but some provisions were considered humiliating. Negotiations broke down, and on July 28, 1914, Austria-Hungary declared war on Serbia. Russia, as Serbia's ally, began mobilizing its military, prompting Germany, an ally of Austria-Hungary, to declare war on Russia on August 1, 1914.
- Chain Reaction of Alliances: The outbreak of war between Austria-Hungary and Serbia triggered a chain reaction of alliances and declarations of war. France, allied with Russia, declared war on Germany on August 3, 1914. Germany responded by invading Belgium, which brought Britain, an ally of Belgium, into the war on August 4, 1914.
Thus, the assassination of Archduke Franz Ferdinand became the catalyst for a series of actions and reactions that ultimately led to the outbreak of World War 1, a global conflict that lasted from 1914 to 1918 and resulted in millions of casualties and significant changes in the geopolitical landscape.