Blocks to ship movement can be added in the adj-provs.csv file. I particularly like how the Third Reich Mod has blocked Channel movement at Dover for Germany and at Cherbourg for England. The Channel Islands should definitely control access to the Bay of Biscay from Channel to the NE. Those big guns at Battery Mirus!
Operation Cerberus, the german channel dash, is a prime ww2 example that in spite of an alarmed enemy a naval force could move through such a blocked area. But Dover should block the movement of german naval task forces in AOD. That would be a simple and easy solution to teach the german ai to use the historical routes to the North Atlantic.
I also like the idea of Crete controlling E-W Agean access because it makes Crete a worthwhile objective for the Axis and also there's always the Guns of Navarone.
The british Dodecanese Campaign is an example that Crete itself doesn't hamper naval movements. It's the presence of strong naval and air forces which inhibits most naval movements.
Also, control of one bank or the other of the Suez should block movement for the other. See the Third Reich Mod for further information.
Control of Suez was blocking movement since HOI1 iirc. But I'll look at that mod to get an idea how they've blocked movement through the channel.![]()
I've looked recently more closely at how the Third Reich Mod modelled closing of certain areas for naval movements. Its idea is to 'channel' naval movements through a land province which, if in enemy hands, does prohibit these.
Therefore I've made possession of Taranto the condition for moving fleets into the Adriatic Sea. The Strait of Otranto and also the Strait of Messina are no longer easily passable. Crete has only influence on naval movements through two of the three available sea zones connecting to the Sea of Crete (north of Crete; needs to be renamed).
re naval movements through the English Channel I've implemented a solution which hampers only the british/allied side. Enemy control of Calais will now stop naval movements through the English Channel. Movements to Portsmouth or Plymouth from the West are as usual. Forces based there can't any longer interfere in the North Sea which now has to be controlled by forces based at Scapa Flow or Rosyth.
Since the Germans heavily relied also on coastal shipping through the Channel I haven't implemented a similar fix for them which would otherwise precluded another channel dash. But honestly if we would force all german naval movements around the British Isles the ai german navy would be destroyed piecemeal which would be no fun either.
These changes and all the other fixed crossings will be available when the next map fix is uploaded. We're now working on fixing IC & resources, too.