The Wiki article about World War 1 notes the following:
The only existing German plan for any war had German armies marching through Belgium. Germany wanted free escort through Belgium (and originally the Netherlands as well, a plan which Kaiser Wilhelm II rejected) to invade France
However, the article does not go into any further detail as to why this was the case, and also doesn't list any sources for this. Is this true, and if it is, why did Wilhelm II reject an invasion of the Netherlands?
As a follow-up question, how did the Dutch defences at the time stack up compared to the Belgian ones, and how would they have faired against Germans marching through?
I can think of two reasons:
Getting the Netherlands involved in the war had no real strategic value to the Germans except for a way through Dutch Limburg so they could avoid the forts around Liége (which stopped their advance for almost a fortnight).
Not getting them involved actually helped them as the Dutch closed of the Scheldt river so no reinforcements could reach Antwerp and the Belgian/English force there had to abandon the city.
Secondly and probably more important: the Dutch royal family and the Kaiser were very closely related. Wilhelmina's mother and husband were both German. The Dutch Queen negotiated with Kaiser Wilhelm several times to keep growing tensions between the two countries under control and to keep the Netherlands neutral.
Not too sure about the Dutch military strength in 1914 but I don't think they would have stand a chance against the Germans.