I actually adopted a different strategy to those listed above. Took me a little while to work out and was closing in on victory when I fell to friendly fire the first time.
My approach:
Flank straight away, bring up the BigTac and auto guns and anti aircraft. Flick the torpedos to starboard. Radar zone 8km and pause...find the opposition DD's. Set the speed of torps to max, giving you about 7000feet range. I had some of my own fleet to leeward but alas they were behind, which meant every man and his dog was gunning for me. I found that I was most successful when there was one DD in front of the others, that gave me time to scamper a bit. Nothing worst then getting blown to bits with no speed to manauver.
Detail everything to south to attack the DD, everything in the north west to attack the other flanking DD. That leaves either four or five in the middle unaccounted for. Patience.
Unpause, give it everything you've got, four fish and head west. (Reasoning to come.) When the first DD sinks, redetail the southern contigency on one of the inner DD's. Redetail 5 inch guns to same ship, detail four inch guns to the nearest PTG. Keep the 4 inch guns on alternate PTG's, they move like flies.
When the second lot of torpedoes come on line, turn, still at flank NW, and look at the nice alley made for you. I couldn't see my opponents as the southern fleet were now between them and I but I aimed in the general direction. I dropped one DD and one PTG over the horizon.
I had the southern fleet move in from the eastern horizon dropping the DD's. When my Uboats finally got into the north, I had both groups join and had about 8 concentrated on each DD. As each dropped, I redtailed the 5 inch guns and the attacking fleet. At the end, I was left with 4, their DD's were gone and the PTG's were to be moped up. As each of the PTG's moved in on me, I had the AA 40 and 20mm guns lend assistance. I left none in reserve to protect the KW3.
Eventually, the Kw3, couple of u boats, one of my DD's were left to mop up the 3 submarines. I hit the yellow sub on the first pass and picked up one of the others as well before calling it a day.
Opinion: the drop helped me the most. If I could get one or two of my surface boats in front of me to take the pummelling, I was prepared to sacrafice them for the good of the fleet.
This mission subsequently meant I have completed all 6 campaigns. This was perhaps the second hardest cognitive mission, the USA surface one (protect the convoy?) perhaps beating it by a whisker. The LFN sixty second drill with the subs required the most tactics.