[HundertzehnGustav]

The subs were a threat.
That threat was kicked in the balls by whom? surface and air.
so who is the major player in the atrantic? the DD, the PBY or the VII?

The subs were dangerous, and scary as hell.
but too few were active, and the intel was soon known.
control, in the sense of controlling who is using that space (2D or 3D) over a given timeframe.........
the subs never managed to do that.

so the subs never controlled anything. not the large areas, not the channel. Not the rivers and harbors, not the convoy routes.
because the enemy poured more and more ships on that battlefield.
The subs didnt even control their own front garden, the bay of biskay after 1942.

subs never controlled anything.