@simon33:
I don’t reckon the rules are clear on that one…
…since there is indeed no escorting warship for the assault.
Maybe here is a misunderstanding: The requirement of an escorting warship is not ‘bound’ to the assault itself that takes place in the Conduct Combat Phase. It is a requirement for the Combat Move Phase, see again:
@rulebook:
However, a transport
is not allowed to offload land units for an amphibious
assault in a sea zone containing 1 or more ignored enemy
submarines unless at least 1 warship belonging to the
attacking power is also present in the sea zone at the end
of the Combat Move phase.
Pretty clear, as I think.
This is only the rules of course, I do understand that you do not feel comfortable with that.