In 1914 the King of Belgium declared: "Belgium is a nation, not a road" in response to the German "request" to send troops through to fight France. Now, we all know how that turned out. However, what if Belgium's courage wavered and their leaders (at least those who had the firmest hold on the levers of power) doubted that England and France could help. What if they secretly gave consent for the German armies to march through?
Option A: the Agreement is kept secret, the French and British learn only too late that the Germans are coming. As a result, Britain, throroughly disgusted with Belgium refrains from using the presence of German troops as a casus belli. After all, the King has himself renounced Belgian neutrality. The UK does not declare war in 1914, though tension between Germany and Britain will rocket to levels unseen before. The von Schlieffen Plan works (or at least the Germans do a great deal better because they are able to move faster without conquering Belgium).
Option B: France catches wind of the Belgian capitulation, they ( and possibly the Brits) send troops into Belgium to meet the advancing columns. They are driven out as the Germans advance into northern France, but Belgium is more and more under German influence. In fact, the nation's industry and agriculture is put to work for the German war effort, and for all intents and purposes they are allies (albeit unwillingly) of the CP.
Thoughts? Your own ideas if this happened?