Quick Decision can save the base in Panzer Quest. This is the video of the Panzer Quest defence situation.
I had this kind of situation many times in Panzer quest, Panzer Rush or other games like that. You just need to act fast. There is no point in thinking too much because sometimes you just don't know the outcome, and even though it may feel that you will lose, you just don't know what the enemy has and you may be very surprised how little the enemy is prepared for the defence.
Playing Panzer Quest or Panzer Rush, you always have to have a strategy in hand and be able to use it at any time.
I have won many battles like that, and in some of them, I was actually shocked I actually won.
So have some faith and believe in your ability and you will move mountains ;)