The world as we know it is a fragile thing. These photos provide some needed perspective.
A photo series commemorating World War I's centennial merges pictures from the modern world with overlays from the war.
The result is a stunning, beautiful, and somewhat ghostly look at the past.
One of the bloodiest conflicts in all of human history, millions of people lost their lives because of World War I. And while the United States didn't officially declare war on Germany until April 1917, it's estimated that more than 53,000 American soldiers lost their lives in battle.