A Cluster is a Clan military formation typically consisting of between three to five Binaries and/or Trinaries, with an average of four to five Trinaries. The equivalent in most cases to an Inner Sphere regiment, Clusters are commanded by Star Colonels, often leading their unit from an independent command Star or Nova. In general Clusters are combined-arms units since fighting at this scale of combat requires an effective mix of forces, though how each Clan organizes their units varies greatly. On average a "typical" Cluster would consist of two OmniMech Trinaries, an Elemental Binary, an OmniFighter Binary and either a mixed Trinary or a Supernova Trinary.
So-called "pure" Clusters, consisting of Binaries and Trinaries of all one unit type, are less common but not unknown. Pure 'Mech and fighter Clusters are rare and most cases temporary, though with the latter some Clans do maintain dedicated formations as part of their front-line units, particularly for naval escort. Elemental Clusters are even more rare, formed typically for temporary special assignments, with some Clans assigning an OmniMech to the command Star for transportation purposes. Conventional armor and infantry Clusters are virtually unheard-of among the Clans.
- Field Manual: Warden Clans, p. 12
- Field Manual: Crusader Clans, p. 10
- MechWarrior's Guide to the Clans, p. 75
- Classic BattleTech RPG
- Field Manual: Warden Clans, p. 10
- Field Manual: Crusader Clans, p. 8
- Field Manual: Warden Clans, p. 11
- Field Manual: Crusader Clans, p. 9