So, if a transport moves to a SZ and joins a warship there and then both move to a SZ containing an enemy sub the sub will not fire?
Though that specifically wasn’t covered, that I saw. My bet is the transports are protected in that situation as well.
The warship and transports start at a naval base, move into a SZ containing a sub, move together out of the SZ, then split up for their third move. Obviously, the transports should still be protected, even though they weren’t accompanied for their entire move.
Regarding hobbes’ question I could see it covered either way: NO, because all moves occur simultaneously, in which case you can never move to meet something, as that unit started moving at the same time, thus, unless you start together, you don’t move together. This seems to me to be the correct strict interpretation of movement rules. EDIT: I believe this is further implied in the rules of AA50 Mechanical infantry and Paratrooper tech where infantry need to be in that same starting place to be picked up; not along the way.
HOWEVER, it could also be flimsily justified that moves aren’t QUITE simultaneous, you can play catchup, and fleets are considered in convoy (and transports protected) if a group of ships the cross the same boundary together. Thus, you move a BB to meet a transport, then move the two together into a seazone. If this is the case, then I think the transport should be REQUIRED to burn it’s first move space as it was waiting (which isn’t a rule anywhere but would make sense). Otherwise you could abuse this protection by moving the BB to the transports spot, move both one space (under convoy cover), and then move the transport one space further. And that’s bogus because that’s completely counter to how carrier/plane movements work (completely independent and occuring at the same time, thus planes don’t get carrier movement plus air movement).
So, I’m going to guess that you simultaneously start all movement regardless of how far a unit will travel and that means if you don’t both start in the same seazone you can’t get transport cover.
EDIT: That said, maybe it would be possible to have both start in different spots, move to a single seazone, move together across the same seazone boundary to an enemy sub location, and then (possibly if starting at naval bases) move their final 3rd space. I could maybe see that as a legal move, as they both started at the same time and moved across the Sub’s seazone boundary at the same time (on the same move: space 2). But it seems simpler as a rule to say that if they don’t start as a convoy, they aren’t a convoy (seazones are really big, it takes a while to get to the same spot), and only “join” at the end of the turn, and that whatever warship is escorting the transport is required to stay with the transport that entire move and cross all the same seazone boundaries together.
It doesn’t seem as though you could escort a transport through a zone, and let it go IN THAT zone to go on to another one alone while your destroyer does a hard to port and goes somewhere else. Seazones are big, and the most efficient route is actually breaking up the convoy halfway through the enemy subs seazone to steam 90 degrees to a different one. I think you’d need to enter and leave with that transport through the entirety of that seazone that the sub is in.