@Krieghund:
You can’t retreat when there’s nothing to retreat from. As soon as the only valid targets are transports that cannot retreat, combat is over and the transports are removed.
Great, that definatively addresses the first scenario (subs against transports and planes). How about the other two scenarios?
We know that attacking transports are allowed to retreat (if able). We also know that carriers are allowed to retreat (if able). So when the attacker only has subs and transports, and the defender only has planes and transports, combat must proceed as normal, correct? Both players are rolling against transports on both sides until either attacker retreats transports from planes or attacker no longer has transports and then defending player immediately removes their transports?
Based on how spare hits end up being allotted to transports in standard combat, it seems as though this kind of battle would be resolved this way, and there are still valid targets on both sides: subs can only hit transports, but the attacking transports CAN retreat, so combat is not over until the attacker retreats.
The carrier condition:
Subs and carriers vs planes and transports.
Surely, combat proceeds as normal, subs rolling against transports while planes rolling against carriers? If the carrier was replaced by a battleship, it’s obvious that that is how the battle would progress, all subs hitting the transports with the BB and planes duking it out until attacker retreated or defender lost the planes.
That must mean that if the carrier is replaced by transports (example 1), attacker and defender are both rolling on transports and it’s a race in hits to see if the attacker can retreat from the planes before losing all transports? There are valid targets for both, and the attacker is retreating from something - planes hitting transports (or carriers).