Manual on Swedish ?

@The_Good_Captain Yes, it’s legal.

@Mn-guy As your question is neither about the website nor the forum itself I have moved your topic to the A&A Classic Forum Category,

Is Eire and United Kingdom adjacent by land …

No.

… or you need a transport between the two?

Yes.

@Mn-guy Yes, other units can participate in the sea battle. Other than being a prelude to an amphibious assault, it is just like any other sea battle. The rules on page 15 mention only battleships and transports because they are the only units that can participate in the land battle.

As a side note, attacking air units must, of course, be assigned to either the sea or the land battle, as indicated by where they end their combat movement. They cannot participate in both, even if the amphibious assault is against an island.

@Krieghund Thanks! (For completeness, I should have been more clear in that Germany controlled Persia at the beginning of its turn in this example. i.e. there was/is a legal landing zone for the fighter)

@coachdcj Player 2 is correct. From the Official Rules Clarifications document (page 4):

You can never give an ally anything: units, territories or I.P.C.'s.

@The_Good_Captain
Thanks Cap

@thecabal

The practical application in an actual game is the following:

This can adversely affect naval battles with multiple unit types on both sides and land battles in which the defender has a bomber(s) or a defense with multinational forces present.

It can cause the defender to misallocate his hits not knowing if the attacker is going to roll hot, cold or par.