Consisting of a system of interlocking modular fortifications, the Castellum Stronghold is a Space Marine tactical fortification intended for front line use.
Deployed from orbit by landing craft, it can be swiftly configured and assembled even under heavy fire. The individual components are deployed in drop
cradles clad in ablative armour, the remnants of which are jettisoned at the moment the sections are landed, revealing a fully operational stronghold.
Such is the skill of the Legiones Astartes that in battle conditions this might take as little as 30 minutes, while the most adept at such operations, in
particular the Iron Warriors and the Imperial Fists Legions, take great pride in reducing this timeframe even further.

Castellum Strongholds are generally deployed for short lived but high intensity operations where the Space Marines must establish a heavily fortified
base in highly contested war zones. In such conditions it can serve as a firebase, artillery redoubt, defensive strongpoint, or platform from which they
can launch immediate offensive actions. It is not an unknown tactic for a Castellum Stronghold to be dropped deep behind enemy lines during an ongoing
battle, sowing confusion and forcing a foe to turn back on themselves to stop their deployments from being destroyed from within.