Courtesy of the Library of Congress.
No Man's Land
The stretch of land between the front line trenches was dangerous. No Man's Land contained miles of barbed wire, hundreds of corpses, and land mines. Sometimes as narrow as 15 yards or as wide as several hundred yards, No Man's Land was heavily guarded by machine gun and sniper fire. Soldiers were forced to cross No Man's Land to advance or scout for enemy positions. Official truces were often necessary to retrieve the wounded or bury the dead.
Gas
First introduced to the battlefield in 1915, poison gas was a constant threat in the trenches. Gas could kill quickly or cause permanent damage. Because gas was often released when the winds seemed favorable, situations could quickly backfire if the weather changed.
The Germans had first used chlorine gas during the Second Battle of Ypres. Soon, armies were making use of phosgene and mustard gas. Mustard gas caused severe burn-like blisters when inhaled or in contact with the skin. Since gas was typically denser than air, those most affected were nearer the ground, in the trenches or wounded and unable to move.
On March 20-21, 1918, the Germans fired approximately 400 mustard gas shells into the American lines. Tragically, the men of the 42nd Division had received little training in how to deal with gas attacks and suffered 417 casualties.
