If Japan attacks J1, putting the US at war, do they have a Major IC to place with US1? Or does it happen during the collect income phase, like the bonuses, making it operational US2?
Only the relevant part from the rulebook (Europe 1940.2 page 21) ;-)
Transporting Multinational Forces: Transports
belonging to a friendly power can load and offload
your land units, as long as both powers are at war.
This is a three-step process:
You load your land units aboard the friendly
transport on your turn.
The transport’s owner moves it (or not) on
that owner’s turn.
You offload your land units on your next turn.
The ICs become major the instant Italy declares war on the US, which is BEFORE it conducts combat. Thus, when Italy captures EUS, it has a major, which is immediately downgraded as per the “captured majors become minors” rule.