Although there is some debate about the true number of World War I casualties, the U.S. Department of Justice estimates that a total of 5,142,631 souls perished during the war. Russia lost the highest number of people, with 1.7 million people or 76.3 percent of its armed forces killed, while 116,516 American lives were lost.
The number killed is not the whole picture when it comes to World War I casualties, as 4,121,090 people were either taken prisoner or declared missing and another 12,800,706 people were wounded during the war. Not all deaths reported were a result of battle wounds, however. For example, the death toll of American soldiers includes 63,195 soldiers dying from disease and accidents and 53,513 deaths on the battlefield.