All combat moves are commited at once. You determine where you will attack and with what. The attacker decides which battle will be fought first and as soon as dice hit the table that is it– no going back and no changing your mind. You must fight at least one round in each of your declared combats.
Each combat is finished-- defender destroyed, attacker retreats, both destroyed before you move to the next one. Where there are fights and what will fight must be determined first.
@texlawman:
…unoccupied hostile territory. I then tried to attack Russia with my forces in Caucuses and some tanks that I had held out of the first battle …
Since the first battle was resolved the tank should be able to blitz and join then next battle in Russia while claiming the unoccupied hostile territory.
This is not a legal move. That tank has missed its chance at combat this turn.