The naval unit re-supply table can be found on page 89 of the Manual and essentially it is a function of the strength of the port and the distance of the unit to the port.
For example, if you have a naval unit at 0 supply, and the port is at strength 5, and your naval unit has returned within action point range of the strength of the port, e.g. within 5 hexes of a port that is at strength 5, then the following cases could apply:
- Naval unit has returned within 4 hexes of the port, the naval unit will now be at 6 supply, e.g. 10 - 4 = 6
- Naval unit has returned within 3 hexes of the port, the naval unit will now be at 7 supply, e.g. 10 - 3 = 7
- Naval unit has returned within 0 hexes of the port, the naval unit will now be at 10 supply, e.g. 10 - 0 = 10
A port, unless by an event, will never remain at 0 for your opponent as the resource strengths are re-calculated at the end of your turn, so on their turn at a minimum it will always be at strength 1. So yes, even a port knocked down to 0 will still provide maximum supply as long as the naval unit returns directly to the port.
The benefit of knocking down a port does require the unit to return all the way back to port in order to receive a good return supply value, but it does not fully eliminate supply as mentioned here.
Could this change?
We'd have to think about it carefully as I do see what you are after here, but at the same time we don't want to introduce a situation that we haven't considered that would also be affected by any change here.
< Message edited by Hubert Cater -- 11/21/2020 2:27:55 PM >