The event commonly referred to as the start of the Great War, or World War I, is the assassination of Archduke Franz Ferdinand of Austria on June 28, 1914. The archduke was killed in Sarajevo by Gavrilo Princip, a member of a nationalist group seeking independence for Serbia from Austro-Hungarian rule. This assassination set off a chain reaction of alliances and military mobilizations, leading to the war's outbreak in July 1914. The assassination intensified existing tensions between major powers, including Austria-Hungary, Germany, Russia, and France, culminating in a widespread conflict that lasted until 1918, reshaping the geopolitical landscape of the 20th century.