Formations are a special type of Detachment, each a specific grouping of units renowned for their effectiveness on the battlefields of the 41st Millennium. Whilst some Formations provide you with all the gaming information you will need to use them in your games, it is not uncommon for them simply to describe a number of special rules that apply when you include several specific units together. Instead of including a Force Organisation chart, the Army List Entries that comprise a Formation are listed on it, along with any special rules that those units gain. Unless stated otherwise, each individual unit maintains its normal Battlefield Role when taken as part of a Formation.

Unlike other Detachments, Formations can also be taken as part of Unbound armies (pg117). If they are, their units maintain the special rules gained for being part of the Formation.

There is no limit to the number of Detachments a Battleforged army can include and you can use any mixture of Detachments you have available, within the restrictions of the rules that follow. However, all of the units in your army must belong to a Detachment and no unit can belong to more than one detachment.