World War I was unlike any conflict the world had ever seen. From 1914 to 1918, the Central Powers of Germany, Austria-Hungary, Bulgaria and the Ottoman Empire were locked in a grueling battle against the Allied Powers—Great Britain, France, Russia, Italy, Romania, Japan and the United States.
The advent of new military technologies during the war and the associated horrors of trench warfare led to unprecedented levels of carnage and destruction. By the time the war was over and the Allied Powers claimed victory, more than 16 million people—soldiers and civilians alike—were dead.