I noticed it was your first post after I answered:
Welcome!
We all love 1940 here, so glad you are playing it.
I was wondering, can a sub move through a convoy and attack on the same turn? Can any other units do it, either allied or axis?
I believe the answer to both questions is “yes”. It’s kind of like a tank “blitzing” through 2 territories. Naturally if there is an enemy unit in said territory, you’re staying put, my friend.