World War I took place between 1914 and 1918 and involved most of the world's great powers. The war ignited due to a complex interplay of alliances, militarism, nationalism, and imperialistic competition. The immediate catalyst was the assassination of Archduke Franz Ferdinand of Austria-Hungary in June 1914, leading to a series of geopolitical conflicts. Major powers divided into the Allies (including Britain, France, Russia, and later the USA) and the Central Powers (notably Germany, Austria-Hungary, and the Ottoman Empire). The war resulted in immense loss of life and significant political changes, setting the stage for World War II.