@oztea:
can subs disrupt a convoy in a sea zone where a destroyer is present?
Yes.
@Omega:
A submarine cannot end its movement in a sea zone occupied by a destroyer. A submarine cannot go through an enemy fleet that has a destroyer
The first statement is not true. The second statement is. Destroyers stop the movement of enemy subs “upon entering the sea zone”. A sub may move into a sea zone with an enemy destroyer - it just can’t keep moving through.
@WILD:
My question is if a sub submerged does it still cause damage.
Ah, submerging. One of the things to understand here is that submerging doesn’t work in the same way as it did in Revised. Look carefully through the rules, and you won’t see a reference to submerged subs anywhere other than in relation to combat. In these rules (as well as in AA50 and AA42), submerging does nothing more than remove a sub from combat and place it back on the game board. It has no further effect. Once the sub is back on the game board, the fact that it submerged to escape combat is no longer relevant to anything. You don’t need to turn it on its side, because there’s no need to remember that it submerged.
The only case I can think of where a submerged sub has an effect on subsequent events is during an amphibious assault, and even that is combat-related. If there’s a sub in the sea zone and you choose to attack it, it may submerge (assuming you don’t have a destroyer). Because the sub submerged, it won’t block your assault even though you attacked it and didn’t destroy it. This effect is momentary and is resolved between the sea and land battles of the assault, so there is no need to remember that the sub submerged beyond that point.
We actually considered changing the term “submerge” to something else to avoid confusion with the Revised rules, but we couldn’t think of anything appropriate. I wish we had changed it, as it’s always been a source of confusion, even in Revised. After all, subs don’t really fight on the surface, do they? They’re nearly always submerged in combat. The term “submerge”, as it’s used in the game, really refers to diving deep, as opposed to remaining near the surface where it can attack and be attacked.
So the answer to your question is: It doesn’t matter, as subs aren’t “submerged” during the Collect Income phase.
@KH:
Still, why must convoy disruption be “declared”, if it’s no part of the combat fase?
If you have a ship in a convoy zone adjacent to a territory controlled by a power with with you are not at war, you may not wish to disrupt its convoy. Doing so will result in war.