Newbie Question: Attack Benefit

[Renojustin]

A fort does not bring resources to surrounding provinces, it takes a percentage of resources from surrounding provinces based on its Admin rating. It DOES propagate supplies to neighbors however. Big differece.

And it usually takes more than 1 fort to take half or more of the resources from a neighboring province to the point where it starts reducing available resources for building in that province, unless one is a capital.