There WOULD be a battle in Hawaii even though the hypothetical fighter scrambled and defended against 10 carriers which had no attack value.
The fighters are required to attack for at least one round, even though the amphibious ground units didn’t make it to the party.
So in this example, where the attacker clearly didn’t understand the rules or made a big oversight, the fighter scrambles.
I’m assuming, like Krieghund did, that the fighters over Hawaii only have 1 movement point left.
Retreating the carriers from the fighter (because it’s a losing proposition) would save the carriers and transports and ground units (at least until USA’s turn!). They would all have to retreat 1 space to a sea zone along a path that they attacked from.
The 20 fighters over Hawaii are doomed because there is no landing space, so the attacker should attack until all attacking or all defending units are destroyed.
Wild Bill is mistaken in saying the land battle wouldn’t happen. The battle in Hawaii MUST happen (at least for one full round) because the attacker legally made a combat move of 20 fighters to Hawaii. It’s only the attacking amphibious ground units that will not be attacking Hawaii, but retreating and staying on their transport(s).