American soldiers react to a gas attack in an undated photo, likely used for training purposes, taken during the First World War. (Photo by Reuters/Courtesy Library of Congress)





An American gun crew from Regimental Headquarters Company, 23rd Infantry, fires a 37mm gun during an advance against German entrenched positions. (Photo by Reuters/Courtesy Library of Congress)





American soldiers keep watch in a trench in France in an undated photo taken during the First World War. (Photo by Reuters/Courtesy Library of Congress)





American, British, French, and German gas masks are seen in an undated photo taken during the First World War. (Photo by Reuters/Courtesy Library of Congress)





Two American soldiers, Corporal Howard Thompson and James H. White, who were part of a group that killed and captured several Germans in no man's land. Thompson holds a pistol taken from a German soldier killed by White. Photograph taken in Ancerviller, France, March 11, 1918. (Photo by Reuters/Courtesy Library of Congress)





An American Expeditionary Force doctor tends to an injured American soldier immediately behind the first trench line in France, in 1919. (Photo by Reuters/Courtesy Library of Congress)





American soldiers move equipment along a dirt road in Saint-Ouen-les-Parey, France, February 1918. (Photo by Reuters/Courtesy Library of Congress)





Wounded lie in an American field hospital in Auteuil, Paris, France around 1915 during the First World War. (Photo by Reuters/Courtesy Library of Congress)





American soldiers charge an enemy position in an undated photo taken during the First World War. (Photo by Reuters/Courtesy Library of Congress)





American forward observation posts are seen during World War One near Forges, France. (Photo by Reuters/Courtesy Library of Congress)





American soldiers practice throwing hand grenades at enemy positions in Choloy, France, August 1, 1918. (Photo by Reuters/Courtesy Library of Congress)





U.S. Army soldiers playing baseball in France in 1917. (Photo by Reuters/Courtesy Library of Congress)





A U.S. Marine leads training on a shooting range in France in an undated photo taken during the First World War. (Photo by Reuters/Courtesy Library of Congress)





American soldiers from the 1st Division are deployed in the First World War. (Photo by Reuters/Courtesy Library of Congress)





U.S. soldiers of the 82nd Division stand in formation at Camp Gordon, Georgia in 1917 for service overseas. The division would later become the legendary 82nd Airborne Division. (Photo by Reuters/Courtesy U.S. Army)





American troops undergo grenade gun training in France during World War One. (Photo by Reuters/Courtesy Library of Congress)





American soldiers of the Machine Gun Battalion, Company G, Second Brigade, gather around an outdoor kitchen in Hermitage, France, March 11, 1918. (Photo by Reuters/Courtesy Library of Congress)





An injured soldier is loaded into a U.S. Army ambulance in an undated photo taken during the First World War. (Photo by Reuters/Courtesy Library of Congress)





U.S. Marines form a line in France in an undated photo taken during the First World War. (Photo by Reuters/Courtesy Library of Congress)





American troops march down a road in France in an undated photo taken during the First World War. (Photo by Reuters/Courtesy Library of Congress)





Princeton University students who have enlisted in military service learn about trench construction during World War One. (Photo by Reuters/Courtesy Library of Congress)





Soldiers of the U.S. Army 27th Division parade in New York City after their arrival from France. (Photo by Reuters/Courtesy Library of Congress)





American soldiers of the U.S. Army 27th Division react after arriving in New York City from France on the ocean liner Leviathan, March 6, 1919. (Photo by Reuters/Courtesy Library of Congress)





U.S. soldiers return to Washington, D.C. following service in the First World War. (Photo by Reuters/Courtesy Library of Congress)