Battles are fought between two sides and each side is normally represented by a single player. You can involve several players on a side if you want, one player acting as overall commander while the rest help him to move troops and roll dice. In the game rules and descriptions that follow we assume that each side is represented by one player.
Before you are ready to fight a battle both sides must choose their forces. If the game is part of a pre-planned scenario (like the Battle for Maugthrond Pass) the forces are pre-determined by the scenario itself. Scenarios for Warhammer are published occasionally in White Dwarf and we have several new ones in preparation. However, if you want to fight a straightforward battle between two players you will need two armies.
The contents of the Warhammer box provide you with two reasonably sized armies, but the chances are you will want to start a model collection of your own which you can field in battle. You may wish to use the models you already have to form the basis of a larger army of High Elves or Goblins.
To keep things fair every type of warrior and monster has its own points value. The better fighter a model is the higher its points value. If a model carries extra weapons, or wears armour, its points value is increased. If it rides a horse, giant wolf or war boar its points value is increased further. When fighting a battle both sides choose armies to the same total points value.
A reasonably sized battle is provided by 1000 points on each side, and such a game can be resolved within an evening. A larger 2000 point a side battle will take a little longer, but can still be fought in half a day or a long evening. 3000 points will give you a fairly big battle that will probably take a full day to fight. You can fight any size battle you like, from a few hundred points a side to many thousands if you have space and time!
While discussing armies and points values we ought to mention the Warhammer Armies series of books. Each book describes a particular army such as High Elves, Dwarfs, The Empire, and so on. Each book provides you with a description of the army, detailed special rules for using it, a painting guide with shield and banner designs, and an army list. The army list defines which troops the army may have and what weapons they can carry.