The Americans are coming, but will the war be over by the time they get there? Germany throws everything into a last series of stupendous attacks in the West while hoping to avoid getting burned by a fire in the East they helped fan.
Machine guns, barbed wire and millions upon millions of artillery shells create industrialized meat grinders at Verdun and the Somme. There's never been a human experience like it and it changes a generation.
The war of maneuver that was supposed to be over quickly instead turns into a lingering bloody stalemate. Trench warfare begins, and with it, all the murderous efforts on both sides to overcome the static defenses.