The reason behind the collapse of the Schlieffen Plan was that the plan itself was very dependent on the rapid deployment and the Germans underestimate the Russia and the Belgium was resisted to the plan. So, in this plan, there are 3 countries that responded in different ways, the Belgium, Britain, and France. For instance in Belgium, even though the German didn't expect resistance from the Belgium, but the Belgians managed to delay the Germans' advance.
