Warhammer allows you to fight battles with armies of troops, war machines and monstrous beings. It is up to you as the commander of your forces to find the best way to use your cavalry and infantry to achieve victory. The Citadel miniatures used to play Warhammer are simply referred to as models in the rules that follow. Each model is an individual playing piece with its own capabilities and characteristics.

In most cases, models band together into units. A unit will usually consist of several models, but a lone heroic character, a single, very large and powerful model such as a chariot, a monstrous creature like a Dragon or Great Cannon and its crew are also considered to be a unit.

Units have different capabilities and are divided into several types as explained below. For example, when the rules refer to cavalry units, all troops that fall under the category of cavalry must follow those rules.

Units are arranged in a formation that consists of one, two, three or more ranks. As far as possible, the unit always has the same number of models in each rank and, where not possible, it is always the rear rank that is left short. The last rank is filled from the centre.