Ace the UK Citizenship Test 2026 – Unlock Your British Adventure!

The event commonly referred to as the trigger for the First World War is the assassination of Archduke Franz Ferdinand of Austria. This event occurred on June 28, 1914, and it set off a chain reaction of political events and alliances that quickly escalated into a full-scale war.

The Archduke’s assassination by Gavrilo Princip, a member of a nationalist group seeking the independence of Serbia from Austro-Hungarian rule, heightened existing tensions between Austria-Hungary and Serbia. In response, Austria-Hungary issued an ultimatum to Serbia, which, due to various alliances and treaties among European powers, prompted Russia to mobilize in defense of Serbia, leading Germany to declare war on Russia and subsequently involving other nations.

In contrast, while the sinking of the Lusitania and the German invasion of Belgium were significant in the context of the war, they occurred after the war had already begun and played more of a role in shaping public opinion and involvement, particularly for the United States. The Treaty of Versailles, on the other hand, was a peace agreement that ended the hostilities of World War I, not a catalyst for the war itself. Thus, the assassination of Archduke Franz Ferdinand stands out as the key