The Allied Plan: dislodge the Germans from their forward trench lines by attacking over the open stretch of ground known as no-mans land. Once a forest, the trees have been leveled by heavy artillery bombardments.
The German Plan: Hold back all allied attacks by raking the empty expanse of no-man's land with machine gun fire the moment the Allied soldiers come out of their trenches.
Attacks against trenches were often met with failure. Here, French troops in 1916 are mown down by machine gun fire in an attempt to break the German lines in the battle for Verdun, France.
Americans also had machine guns. Here, an American in a machine gun nest keep watch for a suspected German attack in 1918.
Launching the attack! In the trench lines of Northern France, Allied soldiers go over the top in an attack against the German trenches across the field. Armed with rifles with attached bayonets, American infantrymen charge in the foreground while French soldiers attack from their lines in the background, recognizable by their bluish wool coats.
Now, as the Allied soldiers launch their attack, a German sentry spots movement from his post and quickly alerts his comrades.
This German is armed with a Mauser bolt-action rife. Near his hand rests a hand grenade with a wooden throwing handle, often called a "stick grenade" or "potato masher".
The Allies press on through a storm of shot and shell, while the Germans try to thwart their efforts.
Driving the Germans out, Allied soldiers race down the zig-zagging earth channels to flush out the enemy.
Clearing the trench of the Germans, the Allies have gained a toehold in the German trench system. Even if they only captured twenty-five yards worth of German trench line and hold it, it is considered a tentative victory.