Germany launches the Spring Offensive, a huge attack to win the war before the Americans arrive.
German General Erich Ludendorff planned a knock-out blow in 1918. He knew the Americans were on their way.If he didn't beat the British and French before the American arrived, he knew the Germans would be outnumbered.
His plan, known as the Spring Offensive, came in several phases. Each time the Germans made good progress, advancing several miles, but each time the Allies were able to get enough reinforcements forward to plug the gaps that the Germans made in their lines.
By July the Germans were launching their fifth offensive but by now American soldiers were arriving at a rate of about 300,000 per month. These vital reinforcements helped the Allies to launch ever more powerful counterattacks. German casualty figures were getting higher and higher.
The Spring Offensive costs Germany too many casualties. Meanwhile American soldiers are now flowing into France.
In the middle of July, French, British and American troops launched a counterattack that became known as the Second Battle of the Marne. They were attacking a salient - a thin area of land bulging into Allied territory that had been won during one of the German offensives.
Now it was the Allies' turn to go on the offensive.
German stormtroopers move forward ready for the Spring Offensive.
French soldiers with a huge naval gun mounted on a train.
A German soldier emerges from his camouflaged position during the Second Battle of the Marne.
A British soldier taken prisoner on the Western Front.