[THEBERBSTER]

hi b
The missions are all date orientated.
They come on and drop off the map whether you request them or not.
It is not compulsory to request missions although you are rewarded for completing in the form of crew bonus points.
Breaking the Fortress (BTF) will usually appear after you have probably requested the coastal mission,
Diverting to do BTF will still add tonnage to your game as you see in the Captain's Log and go towards your Career and boat upgrade.
At anyone time you can have 3 missions showing on your map.
Post #64 Open Horizons II > Campaign Dates > Bases > U-Boats > An Essential Guide
You can request anyone of these missions as many times as you wish until it completes its date and drops off the map.
Peter