WI Mance takes Castle Black

[TMIFairy]

If this topic had been discussed already please give me a kick in the right direction.

I've been reading fics based around the idea of "Jon leaves the Wall before taking NW vows to join Robb's army".

This IMO leads to the fall of Castle Black to Mance's attack as there was nobody to tip off the defenders of the Then infiltrators' attack from the South.

What are the aftereffects of Mance taking Castle Black?

For simplicity let us assume that all other things stay the same - Theon and later Ramsey took Winterfell, Robb was killed at the Red Wedding.

Stannis arrived at the Wall but is too late to save Castle Black. Or is he?

[Lion of the West]

I would think that Wildlings wills stream into the North and it may well lead to the North rallying around the Boltons to face this. And if Stannis would join forces with the Wildlings I think it would be a major PR boon to the Boltons, not to mention that the ploy to get Stannis to besiege the Dreadfort may well work as Jon may not be in a position to advice Stannis against it.