1918, France. The Germans have just been defeated in a massive Allied counterattack, after their own attack stalled a few kilometers away from Paris. The Allies are pushing the Gerrmans back. Even Ludendorf seems to be accepting the defeat.
However, the Germans retreat into the Hindenburg Line. In our world, the Allies plowed through it. However, what if the Hindenburg Line held? What if trench warfare came back?
How could this happen? How would this affect the course of the war?