Ah never mind my previous comments, Kriegshund has it correct. There’s a special rule just for this scenario:
“An attacking land unit can assault a coastal territory
from an ally’s transport, but only on the turn of
the attacking land unit’s owner. All of the normal
requirements for transports offloading in a sea
zone must still be met by the attacking power (see
“Special Combat Movement, Transports”, page 16),
and any scrambled air units will prevent the landing
if they cannot be destroyed”
chances are you’re going to lose the battleship you took to the channel in the opening attacks, which leaves your Baltic fleet pretty thin
You can also use the battleship for the SZ 111 attack and retreat it after one round. The British are then typically left with a damaged battleship that can’t escape because SZ 111 has no harbor.
That is usually where I send the German battleship, SZ 111. My attack on the Channel is all planes and maybe a couple of subs. Although, it has backfired on me when the fighter in Scotland doesn’t scramble and I get very good hits as Germany and end up sinking all the UK ships. Then my poor battleship is stuck all alone in SZ 111.
A good part of that scenario is it gives UK another target, but they have to commit planes to sink it (usually at least 2). That’s less UK planes bothering me somewhere else.
The only time it didn’t work for me was when my dice went sour on G5 & G6 going into Russia, But the following week it worked and everybody was rolling better, I have yet to try it with the latest 3.9 rules. So much depends on good rolls at key battles and being able to work as an Axis team.