waits... for surface attacks:
In rough seas, on a dark and even moonless night, while moving slowly you can find yourself nearly inside the convoy lanes on the surface without being detected. though that is a little close for comfort.
best tactic IMHO is to start from at least 2000 meters from your intended target. plot your solution for a spread of two torpedoes with shallow or no spread angle at two different ships with the bow tubes. when youre last shot leaves the tube come about hard and fast and put the convoy behind you and make good speed out of there.
when the first impacts occur searchlights and starshells will fill the sky so you better be moving at a good rate of speed to get out of there. with any luck you are by now so far away from the convoy that the starshells and search lights are nowhere near where you are.
the advantage of this method is that it negates any advantage of early war sensors. the enemy pretty much has to see you to attack you - active sonar pinging isnt going to do the DD's any good since it really wont pick you up on the surface. and the passive sonar (listening) would likely not reveal your position either.
best conditions for surface attack: at night (obviously) - rough seas, overcast sky (or no moon) the full moon is nice to help you see your targets but it is also helping them to see you - espeically if the outline of a u-boat slices through the reflection of the moon on the water.
keep your speed down - you cut a huge wake at higher speed - go at it slowly and they will be less likely to see you
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