The assassination of **Archduke Franz Ferdinand** in **1914** was the key event that triggered the start of the **Great War** (World War I). His murder by **Gavrilo Princip**, a member of a nationalist group seeking independence for **Serbia**, set off a chain reaction, as alliances and mutual defense agreements quickly escalated regional conflict into a global war. The assassination ignited existing tensions between major powers, leading to declarations of war and military mobilization. This event is often cited as the immediate catalyst for the complex interwoven political and military alliances that characterized the era, leading to extensive destruction across Europe.