A major element of Nazi propaganda was the so-called stab in the back myth - that Germany had not been truly defeated on the battlefield and had lost the war due to traitors in Berlin overthrowing the Imperial government. What if there had been no revolution, and the Entente had had to occupy a significant part of Germany before it threw in the towel? How long would it have taken them? IIRC in 1918 Belgium had been liberated but there were still parts of France, plus Alsace-Lorraine, under German control.
Also, what effects might this have on the post-war world, focusing on the effects on the UK/France and the post-war settlement?