@Young:
Can transports unload within a sea zone with an enemy sub in it, during the non-combat movement phase?
YES. Subs only prevent unescorted amphibious assault attempts.
Can you upgrade a Minor IC to a Major IC and place 10 units on it within the same turn?
NO. It was not major at the beginning of your turn.
1 lone AA artillery unit is being attacked by 1 fighter, is it possible for the AA gun to be destroyed or is a land unit required? if so, would there be a 2nd combat round seeing as the gun only fires once?
Thanks in advance.
Yes, the AAA gun will be automatically destroyed if the AAA defense roll misses the fighter, because it has no defense value. This would be true of multiple AAA guns as well - think transports. It is inevitable that all of them would be destroyed because the attacking air can roll in perpetuity against 0 defense.
For example, if the Axis move all 4 Italian AAA and 4 German AAA together to a territory with no other ground or air units, the Allies could destroy all 8 of them with a single aircraft, if the single AAA roll misses (is not a 1). Or, the Allies could destroy them all with 2 aircraft, as long as the defense is not snake eyes