The year World War I began is 1914. The conflict started on July 28, when Austria-Hungary declared war on Serbia following the assassination of Archduke Franz Ferdinand. The war quickly escalated, drawing in major powers from around the world into a global conflict characterized by trench warfare, new military technologies, and significant loss of life. The war lasted until November 11, 1918, resulting in pivotal changes in political boundaries, leading to the collapse of empires like the Austro-Hungarian and Ottoman Empires, and setting the stage for World War II through the Treaty of Versailles in 1919.