What is C.A.S.E. in Mechwarrior

CASE is (in short) a system that protects the internal components of a BattleMech. If an ammo storage compartment explodes (Through internal heat, or external damage), the CASE system routes all the damage away from the center of the 'Mech. You end up losing an arm, and usually one side of your torso, but that is much preferred to death.