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but I do think they'd concluded that the Ardennes was enough that the whole French army could get in on the attack, making a defense stance (and an eastern German offensive) utterly foolish, given the proximity of the Ruhr to the Belgian Ardennes.
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At first :
that the Ardennes are a ... "lesser" obstacle is a
Post-WW2-Hindsight assesment, that resulted from the germans passing them (quite to the surprise of everybody else) with what can go as all-terrain or heavy-terrain vehicles of thier time (1939).
NOT a contemporary assessment 25 years earlier.
Due to being heavily forrested as well as sparsly populated and probably most important veery badly developed reagrding logistical infrastructure in 1914 it was not only rendered a MAJOR obstacle for every army, including the germans.
The german 4th and 5th army advanced through the Ardennes in the first 3 weeks a distance of about 50-60 km, roughly about a third to a half of what 3rd army achieved - not to speak of the tour-de-Belgique the 1st army.
YES the southern Ardennes WERE an obstacle in 1914.
Then ... "proximity of the Ruhr to the belgian Ardennes..."
Have you ever tried a look it up at the map maybe with google, using the "terraine" function and assed the ... terrain you are speaking of ?
Its southern part west of Luxemburg quite quickly "meets" the Our-valley, which is a really nasty deep valley, naturally built moat that towards the north blends into the Belgian Eifel which to its north blends into the Northern Eifel ... oh, we have reached the dutch border at Aachen (FYI : the Eifel is a
mountain-range).
And I somehow doubt, that an attack of larger french forces through this region would resemble a sneak-"blitz"-attack and NOT being detected and accordingly dealt (aka defensive preparation with troop moveements via the especially for this purpose built railways).
Moltke wasn't a great general, but he wasn't a gullible fool either. He understood perfectly well that the British weren't going to allow him to violate one inch of Belgian territory, but that they would take the opposite view for the French. That's what alliances and loyalty are all about. So Moltke, being a Prussian general type choses between all in or all out and picks all in, in classic Prussian fashion.
Didn't you just said :
Every square inch of Belgian territory is neutral, or its not.
Esp. due to their global position also opposite the "neutrals" (and not at least before the domestic press) the Brits can't measure with different yard-sticks.
If they allow the french to violate "minor part" of Belgium for their conduct of war they have to allow it the germans at least in the same parts as well.
What would end in a clash of forces at a line reoughly from Marche.en-Famenne to Arlon (google it)