A look at the movement of lines on the western front, the Germans went back in early 1917 and then in early 1918 conducted an offensive that is considered successful, but really ony re-occupied what they had given up. WI they never went back in the first place? What would happen elsewhere if the13 divisions freed up by the new line were left in place for 12 months? How would the March 1918 offensive go if it was launched from the pre Hindenburg line positions?