One thing that a lot of people are confused about, and always have been. TMO is not a realism mod. Yes, there are realistic things in it but that is not the purpose of TMO. The purpose is to make the game difficult!
When Ducimus had a choice of having lots of unescorted merchies sashaying all over the ocean or mixing in escorts with just about all of them, knowing what you know now about his evil mindset
, what do you suppose he did?
Thaaaaaaaaat's right.
And yes, in the early part of the war submarines were sent to places the brass knew would be good jumping off points for a repeat Pearl Harbor attack, not where they knew you'd find shipping. Therefore you'll come up empty on some missions early on in the war. If you think about it, they did the appropriate thing. But it's frustrating patrolling empty ocean.