I hope that this isn't obvious, so here goes.

I make a standard stack of a General, 6 cavalry types, 6 infantry types and 6 archer types and a siege device. An enemy stack might have a maximum of 8 zones around it marked in red when you try to move. If you keep two standard stacks together (stacks A and B), you can place the 6 cav from stack A so that each one occupies one of the red zones and then the remainder of stack A in the 7th red zone. This leaves one last red zone for stack B to occupy and initiate the attack. Assuming the enemy stack loses, which is quite likely considering the odds, then the whole stack cannot withdraw and will be totally annihilated. With enough movement left over, stack A can reform to end the turn. Yesterday, with a couple of extra cavalry, I was able to destroy 2 adjacent enemy stacks at once. For home defense a standard stack with 7 cav and no siege device can envelop and destroy smaller rebel stacks alone.