[seafarer]

Can also depend on the mission. If you are ordered to "patrol" somewhere, you just need to get there and stay long enough to complete the mission. You need not sink anything there, just stay within a 50nm radius of the objective for 2-3 days or so.

If you are ordered to "deploy" somewhere, then you will find that as soon as you reach the objective, you automatically receive orders to engage enemy shipping. Then you need to sink 10,000 tons to complete that second objective, so you'll need at least a few torps to do the job.

I use my stern tubes just like my bow tubes, and prefer to pick up a target, get ahead of it and line up my stern at 90 degrees to it's course and then shoot it as it passes astern (this gets much easier to do after you get surface radar on your boat). If attacking a convoy from a flank, get in close, make the first shots with the bow tubes. Then dive, and go full ahead and try to cross under the line of ships, then surface on the opposite flank and pick out targets for stern shots.

It's also handy to keep a stern tube ready for any escorts that come up behind you, although DD's can often easily shrug off a direct bow hit in the stock game (installing NSM helps deal with that issue, as does using magnetic triggers and setting the torp depth to pass under the bow of the DD before detonating).