Westeros: A Game of Thrones.

[Greyblades]

You can react to issues when you have proper information to base your actions upon. If indeed Frey´s would decide to reject you passing the Twins.I am sure you Stark´s can come up with ideas how to deal with that.

I never really understood that, couldnt Robb have just said "screw it" and walked upstream to the green fork's source and crossed there, or heck they could go around alltogether by heading west of greywater watch and following the forest edge south and end up in the same place.