I think Sarmatian, Louis and Brenus heavily over-estimate the military capabilities of the Entente in 1918. Austria-Hungary might have been broken, but you speak as though the Allies had unlimited reserves of manpower. There would still have been an awful lot of territory to occupy before reaching the German border, too much for the Allies to achieve anyway considering their resources. Similarly I very much doubt that they would have been able to push very far into Germany without severe losses that would have had much of public opinion calling for peace.