A damper/strut that can provide variable damping and spring energy storage and dissipation. One embodiment includes an adjustable magnetorheological damper and a mechanically adjustable fluid spring in association with an internal accumulator. A combination of internal and external electromagnets generate the magnetic fields required to activate internally maintained magnetorheological material so that its apparent viscosity undergoes the desired change for a given disturbance. By controlling the strength of the magnetic fields generated in the device, the damping capacity and energy storage of the compressible liquid spring can be affected to provide a semi-active damper that can both dissipate and store energy. The proposed devices can be coupled with a sensor feedback and a control system to provide fast and accurate response force for a variety of engineering applications.