I'm interested in the definition of "war" here. I'm assuming that a declaration of war is always needed to take another player's SC, but I'm also uncertain about the following possibilities:
1) "Colored" but unoccupied, non-SC, non-home space: e.g., Austria moved into Albania early on, so that space is colored with Austria's tag, but he has moved out since. Italy wants to move in. Does Italy need to declare war on Austria?
2) "Colored" but occupied, non-SC, non-home space: Same thing, but Austria now has an army in Albania.
3) Unoccupied, non-SC home space: e.g., does Russia need to declare war in order to move to Galicia? (What if he does so successfully and then Germany comes in - does Germany have to declare war on Russia, or Austria, or both to move in?)
4) Do bounces count as successful invasions requiring declarations of war? E.g., Russia and Austria are allied (although Russia is ready for a stab). Austria mentions that he will move to Galicia, and Russia doesn't like this idea and bounces the move from Warsaw. Does this need a declaration of war, since Russia never entered Austrian territory?