In early 1918, facing the arrival of fresh American troops, the German leadership launched a last-ditch, all-out attack on France: the great Spring Offensive of 1918. German armies came within thirty-five miles of Paris but never broke through. They were stopped in July at the second Battle of the Marne, where 140,000 American soldiers saw action. The late but massive American intervention tipped the scales in favor of Allied victory.

By September, British, French, and American armies were advancing steadily on all fronts. Not wanting to shoulder the blame, Hindenburg and Ludendorff insisted that moderate politicians should take responsibility for the defeat. On October 4, the German emperor formed a new, more liberal civilian government to sue for peace.

As negotiations over an armistice dragged on, frustrated Germans rose up in revolt. On November 3, sailors in Kiel mutinied, and throughout northern Germany soldiers and workers established revolutionary councils. The same day, Austria-Hungary surrendered to the Allies and began breaking apart. Revolution erupted in Germany. With army discipline collapsing, William II abdicated and fled to Holland. Socialist leaders in Berlin proclaimed a German republic on November 9 and agreed to surrender. The armistice went into effect on November 11, 1918. The war was over.