Security System Units will automatically defend your Base during an attack. The same Units will not defend your Base twice – a Security System can only engage an enemy Unit once before being lost.
When you lose a Security System Unit, you will have to hire a new one to replace it. Security Systems cannot be moved to your Bunker, or sent as Reinforcements.
If you have both Security System and Defensive Units stationed at your Base, their defense will be held in two stages.
Stage 1: Security System Units will defend against their specified Unit types in an attack on your Base. Any Security System used to defend against an attack will be lost.
Stage 2: The remaining enemy Units will fight against the other Units stationed at the Base.
All bonuses that increase the defensive stats of regular Units will not apply to Security System Units.
During an attack, specific Systems will defend first. For example, if the Base has active Universal and Combat Aviation Security Systems, and an incoming enemy attack includes both Combat Aviation and Mechanized Infantry Units. The Combat Aviation Security Systems will defend first and inflict damage on the enemy Aviation Units. After that, the Universal Security Systems will begin inflicting damage on the rest.