The beginning of the Great War, later known as World War I, is commonly marked by the assassination of Archduke Franz Ferdinand of Austria on June 28, 1914. This event set off a chain reaction of alliances and treaties that plunged Europe into war. Nationalism, militarism, and complex alliances between countries were already straining relationships among European powers. Following the assassination, Austria-Hungary declared war on Serbia, leading to Russia's mobilization, then Germany's declaration of war on Russia and France. The war enveloped multiple nations and alliances, causing unprecedented global conflict that lasted until 1918.