Something QUITE vital about WW2 is not clear to me.

HOW you go about "starving/strangling" -- a) Great Britain, or b) Russia.

I notice in the report or the occasional pop-up -- that I can cause "1 STP" damage with the U-boots. One. Per turn. Usually. Now, how does that actually inflict ecomomic pain on Great Britain? I mean, they start out with something like 50 STP (sea transport) points. Sometime down the road they'll have to replenish those diminished points, sure. D-Day aftermath in paricular. And even then, they won't need so many. But how does that threaten their Economy from 1940 to 1943? I just don't get it.

Moreso true WRT the "Murmansk Convoys." There is not even a separate sea-zone that applies is there? Or, a PP/$$$-convoy that goes from Great Britain TO Russia?

If you could explain in more detail how the current schematic actually works, and HOW it can reduce Great Britain and Russia's ECONOMY, I would truly appreciate it.