[Leandros]

If you are north-west of Luzon this is probably meant to be part of the Malaccan invasion force. If it is part of the PI invasion it should eventually turn in to the coast for the landings. I have never played SH4 (even if I have it) so I don't know how correct it is historically. The date you mention certainly correspond to RL invasion of some sort. The first landings on the west side of Luzon was north of Lingayen Bay.

Historically, the Sub force operating out of Manila was quite inefficent.

You should note their course, make a roundabout to your starboard (right.....) and speed ahead of them, even out of sight. After a couple of hours you should be able to go down and get their sound bearings.

Happy hunting!

Fred