Another example where only some defending transports might be sunk is similar to Rorschach’s scenario. Five fighters and a sub attack three cruisers, three transports, and a sub. If all five fighters hit and both subs miss and the attacker takes all casualties on fighters, two transports will be sunk. With only a sub and fighters versus a sub and transport, the attacker could retreat.
Of course, there are any number of ways some attacking transports could be sunk before their fellows retreat. One example is a cruiser and two transports attacking two destroyers. If both destroyers hit, the cruiser and one transport are sunk, then the other transport retreats.
There are two important things to remember. One is that hits are assigned to transports in exactly the same way as they are to other surface ships, except that they are assigned last. The other is that a sea battle is over when all units on one or both sides that can fire or retreat are gone, which means that the attacker cannot retreat at that point. If the attacker still has units with an attack value when the battle ends, all defending transports are sunk. The reverse would also apply if the attacker can’t retreat for some reason.