AA guns can’t load in Combat Phase.
You can load them in NCM a turn before, and choose NOT to unload, then choose to unload in a future non combat.
USA attacked 12 German subs with planes and 3 destroyers and a transport, the planes killed everything but 1 German sub and killed all USA destroyers but not the transports. USA can no longer attack normandy because the sub stops it, but does the German Sub kill the Transport?
Edit: sorry, the sub also submerged with the transport still alive!
Not if it submerged
Zallomallo is right. Because the sub submerged, it no longer blocks the amphibious assault and cannot kill the transport. There was no reason for the sub to submerge, however, as the planes could no longer hit it. If the sub did not submerge, the transport could retreat, assuming it had somewhere to retreat to (if not, it would be lost).