nitpick, entente, not allies.
Anyway, not really. By the time Russians and French are actually marching on German soil, the government (which was at no stage particularly fanatical) would sue for peace and offer whatever term were needed. r if they refused, they would be removed and a peace party would take over. In WW1, Germany was fighting for its place in the sun more then anything else, and that's not a cause that really motivates due-or-die resistance.