When a zombie kills a living soul, an infected body is placed in a battlefield graveyard. This restless soul will eventually rise up as a zombie.
When you move any of your heroes or units through a battlefield graveyard, you automatically burn the bodies, preventing them from ever becoming zombies.
If you are victorious in a combat over a graveyard, the bodies will be burned at the conclusion of the combat.
You must burn all infected bodies that litter the battlefield before a game will end.