World War I began on July 28, 1914, following the assassination of Archduke Franz Ferdinand of Austria. This event triggered a series of political tensions and alliances among the major European powers, leading to widespread conflict. The war involved many countries worldwide, primarily the Allies, led by France, Britain, Russia, and later the United States, against the Central Powers, which included Germany, Austria-Hungary, and the Ottoman Empire. The war lasted until November 11, 1918, and resulted in significant geopolitical changes, countless casualties, and ultimately laid the groundwork for future conflicts.