I can see how this would be confusing considering that when you think of an naval base it is surrounded by aa guns, and espcially considering that through most of the war Germany/Italy had their ships in port…and they didn’t get sunk by naval attack and fought off the aircraft. Giving a sz with a NB to act like an aa gun is the best idea I have seen, still not sold on the idea of navies needing aa guns though, considering there are no ‘meat shields’ like inf, the cheapest naval unit is a sub.
All that may be true, but the game is simplified to depict naval battles as occuring on open sea and not in port.
If something resembling port rules were to be implented in any realistic manner then a number of special cases would need to be made to show how port battles actually happened -
Battleships and cruisers would bombard
Ships in port would have reduced defensive values (they were truly sitting ducks against air raids)
Air would be the only units available to attack - at best it would be unrealistic to allow I class subs into pearl, similarly multiple sub pieces would indicate such an incursion that the port would have subs colliding with each other.
And ports could be mined and blockaded.
And yes, AA guns (although, as always, by the nature of the game pieces, a battleship or destroyer HITTING a plane indicates anti aircraft. It’s just not the same level of antiaircraft screening that the AA batteries indicate.
But that’s such a mess, and it either adds a space and special rules, etc etc.