World War I was a global conflict that lasted from 1914 to 1918, involving many of the world's great powers and leading to significant political and social changes. The war was marked by trench warfare, new military technologies, and the mobilization of entire nations, culminating in the collapse of empires and the redrawing of national boundaries. Its aftermath set the stage for major developments in international relations and the rise of movements advocating for civil liberties and political reform.