This is a simple idea, which can be re-used in a hundred variations.

The attacker is told to go in and destroy target A. The defender is not told what target A is, but the defender does know everything which is on the board. The defender has orders to defend A,B,C,D,E,F and G, and may think that he has far too few forces to manage this. As the attacker moves around the board, he discovers B-G, and these are placed on the board.

The attacker only wins if he has destroyed four of the targets.

My thinking is:

1. This makes the game far more interesting.

2. Were I a senior officer deciding which commander to promote, I would favour the one who, when sent to destroy a fuel dump, returned saying that he discovered a telegraph line, railway line, V1 launch ramp, small tank hospital, radar site, AA emplacement, and accordion factory, and had destroyed them all as well as the fuel dump. The officer who just mentioned that he had seen them on his outing would be passed over for having such little initiative. Similarly, I would promote the defending officer who managed to hold six out of seven vital objectives, against a foe who might well have blown up the lot.