The primary cause of the outbreak of World War I in 1914 was a complex interplay of factors, but the assassination of Archduke Franz Ferdinand of Austria-Hungary is often cited as the immediate trigger. This event ignited tensions between major powers, leading to the activation of a network of alliances. The entangled alliances and rising nationalism created a precarious political situation, where competing interests led to declarations of war between nations. Additionally, underlying issues like militarism, imperialism, and economic rivalries fueled the conflict, transforming a regional incident into a global war that lasted until 1918.