That's a very close interpretation of my ruling in this situation. Thanks for all your input and support Cornelius. I think our campaign can finally move forward !I would interpret it thus:
You could rule that when the Army intensity is below 10 the enemy is pushed back and zones 8 and 9 are now combat zones. In the same situation zones 1 and 2 will probably still be non-combat zones. When the army intesity is above 30 the enemy has pushed you back so 1 and 2 are now combat zones and 8 and 9 are still non-combat zones. In all other cases they are still non-combat zones.