On the battlefield troops don't fight as a disorganised mob of individuals, they fight in properly organised units with officers to lead them. Such units are often referred to as regiments or, in the case of cavalry, squadrons. Units of troops march in disciplined ranks and they are trained to manoeuvre as a solid block.

Generally speaking, a unit is made up of troops of the same type. All the models in a unit will be of the same race, and will have the same weapons and armour as well as the same characteristics profile. For example, you could have a regiment of human archers armed with longbows and wearing light armour, or a unit of heavily armored knights riding warhorses. Although in reality creatures of the same race vary - some are weaker, faster or braver than others, we assume that the differences average out over the unit as a whole.

Units are arranged on the battlefield in a formation which consists of one, two, three, or more ranks as shown below. As far as possible, the unit always has the same number of models in each rank, and where this is not possible it is always the rearmost rank which is left short. Units can change their formation during the battle, but this takes up time and may slow the unit down as described later.