From precedent example:

On planet A there are two areas (1 and 2) each having a unit limit of two. I attack from area 1 into area 2 and also bring two more units from an adjacent planet over and place them into area 2 (whit 4 units in a battle). This is a legal move, for battle?

Yes, it's a legal move (obviously if you have the transport that links the adjacent planets)

Very tnx 4 answer