With bombardments. The ships fire. What they hit is moved to the casualty zone of the battle board. Then the attacking land units fire. What they hit is then moved to the casualty section of the battle board. The defender then rolls his dice for all his units including those in the casualty area. After he has done that the removes his units from the Casualty area. The ships only fire at the start of the first round and the ycannot be taken as casualties by the attacker.
Only 2 fighters per aircraft carrier.
One transport can carry two infantry, or one infantry and one artillery, or one infantry and one tank, or one infantry and one AA gun. The maximum number of units allowed on a transport is 2. 1 infantry and 1 other land unit. The other land unit can be an infantry also.
Units that are loading on a transport MUST be in a land square next to the water territory where the transport will pick them up at. Tanks cannot move and then load onto a transport. ALL units loading on a transport may get on the transport and then get off the transport in the same turn.
Yes you can buy units and place them in latter turns.
Submarines cannot submerge when a destroyer is present. So they can be target by air because a destroyer is present or if no destroyer is present they may submerge. Once they submerge they are placed on the game board on their side. They no longer are considered to be part of any battle once they submerge. They cannot fire at units and cannot be taken as hits. In this state they act as if they do not exist. At the end of the non combat move stage they are then turned upright and considered to have surfaced.