approach the convoy with stealth. at night if possible.
it is best to do this from about a 45 degree angle off the port or starboard bow ahead of the convoy.
when you have closed, very slowly, to within about 1500 meters. fire at the largest merchants within the convoy lanes.
fire at the furthest merchant first working your way to the closest so that you can time the impacts to be relatively close together so that when the first explosion takes place the convoy's evasive maneuvers will have hardly no time to throw off your remaining shots' solutions.
DO NOT watch the fireworks through the periscope.
DO NOT leave the periscope up any longer than you absolutely have to - it can be a radar magnet.
after your last shot leaves the tubes, rig for silent running and set your depth as deep as you dare go.
if possible reverse course and deploy 2 oe 3 decoys on the way down in the turn... drop one decoy at about 30 meters depth, drop the second decoy at about 70 meters depth and drop the third decoy at about 100 meters depth.
creep away at 2 knots or less.
follow the convoy - and repeat the process tomorrow night.
edit: one other thing... you are only going to sink 2 or 3 ships at a time by using this method... it will take a few days to make a few attacks, but in the end you will have probably pecked away at about half the convoy's sending all the largest boats to the bottom at least.
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