Set up the scenery in any mutally agreeable way.
One army should be the attacking army, the other should fight the rear guard. Decide which side will take which role beforehand. Both players should select a 2000 points army.
The attacking army should set up at one table edge. The army fighting the rear guard should set up anywhere along the half way line of the table. The rear guard should face the opposing army, the rest of the army should face the other edge of the table and prepare to leg it...
The game lasts for however many turns it takes for the the entire main body to escape off the table, or die in the attempt.
The army fighting the rear guard goes first.
1000 points of the troops in the army who is fighting the rear guard will try to escape of the table edge, while the other half will attempt to stop the other army catching them up. The General of the army must fight in the rear guard action, not try to escape!
The Rear Guard have +1 leadership, as they are resolute in their defence.
The escaping half all have -1 toughness, as they have been injured in the previous battle. Their moevement value is halved. They must move as quickly as they can to escape off the table edge before the attacking army catch up with them.
Ignore the normal Victory Points system. Instead, award 1 point to the defending army for each 100pts of injured troops escaping off the table edge. Add 2 points if the General of the attacking army was killed in the battle. Subtract 2 points if the General of the defending army was killed.
If seven or more points were amassed, the army fighting the Rear Guard has won. If less then seven points were amassed, then the attackers have won.