The first thing I need to know is how many escorts are with the convoy and do they all have radar?
I have been successful if there are only four escorts to the convoy, two on the beam and one each front and rear-look for the times, as you study them, when they swing out and move away from the convoy on a sweep.
You better be decks awash when you move in.
If more than two on the beam with radar, I back off.
I can't say there is any date when it becomes almost impossible to attack under 4000m on the surface at night. Each convoy is different, if it is too dangerous, I wait for the next one.
