@Der:
Got it -thanks! So then can I legally attack the DD with just my BB and transport, sink it, and use my land based planes that weren’t used there to help in the amphibious assault?
Not exactly. Before any dice are rolled, during the combat MOVE phase, you choose where you want each of your units to fight, but they can only participate in one battle each.
Each plane you send to Egypt to help with the amphibious assault does not participate in the naval combat in SZ15. Each plane you send to SZ15 fights in the naval battle, but cannot participate in the amphibious assault in Egypt.
So, you can risk it, and use only the BB against the DD in SZ15, and have both planes and the units from the transport roll against the UK units in Egypt. Considering the BB has two hits, it’s LIKELY you’ll win, but there’s always a chance you get skunked against the destroyer and your BB dies, in which case you would HAVE to retreat the transport. If that occured, both planes (and any land units not from the amphibious assault) would be required to commit to one round of combat in Egypt before they could retreat.
Does that make sense?