The logic is that you have begun a multipart contingent attack–one that requires clearing the SZ first, having already committed the transports. This is one of the most nuanced situations in the rules–that you have to make sure that you bring enough to guarantee the first battle is a success if you fail to do so–most of your protective units will be dead, and the transports exceptionally vulnerable.
I understand what you’re saying. Logically, however, a failure to clear the sea zone of enemy warships or aircraft would result in the now-unprotected transports turning around, heading back to port and offloading their cargo, not moving one sea zone away to await their wholesale slaughter on the next enemy turn. If that’s the case, why even allow transports to retreat? Allowing them to move one space - easy striking distance for the remaining enemy forces - only delays the inevitable.
The rules-reason you cant unload is that a unit cannot both Combat Move and Noncombat move.
Aircraft do it all the time. If the only reason a transport cannot offload into a friendly territory is because it arrived there after retreating from battle, well…that’s not good enough. I accept that it’s the rule; I’m just saying that it’s an arbitrary rule, not grounded in logic or reality.
For those interested, here’s the scenario that started this topic:
ANZAC amphibious assault on Java. SZ 42 battle involved the following:
JPN: 1 Destroyer, 1 Carrier, 1 Fighter
ANZ: 1 Destroyer, 1 Cruiser, 2 Fighters, 1 Tac Bomber, 1 Strategic Bomber (plus 2 Transports, 2 Infantry, 2 Artillery)
Round 1: ANZ = 1 hit, JPN = 3 hits
Round 2: ANZ = 2 hits, JPN = 3 hits
Japanese fighter remains, lands on Java. ANZAC Transports retreat to SZ 55 and, forbidden (by an arbitrary rule) from unloading into the friendly Northern Territory, await their destruction on the next Japanese turn.