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.

A century on, the magnitude of the impact of the Great War on millions of people’s lives can lose its immediacy. This is especially true since evidence of the fight is largely left to grainy black-and-white photographs and scratchy black-and-white film. Those images can seem distant in today’s world, where war coverage is literally at our fingertips—in some cases available live as it’s happening, and in high definition.

These colorized images help drive home the fact that old photographs and films from the war contain the lives of actual people who witnessed real, unspeakable horrors.