An adapter for use with an electromechanical surgical instrument, said adapter comprising: an adapter housing assembly configured to be operably coupled to the electromechanical surgical instrument; a shaft assembly defining a longitudinal axis between a proximal end and a distal end thereof, said proximal end operably coupled to said adapter housing assembly; a surgical end effector operably coupled to said distal end of said shaft assembly for selective articulation relative to said shaft assembly; an articulation actuator assembly configured to operably interface with a source of rotary articulation motions in the electromechanical surgical instrument when said adapter housing assembly is operably coupled thereto to apply axial articulation motions to said surgical end effector to move said surgical end effector into a desired articulated position; and a firing member assembly configured to operably interface with a source of rotary firing motions in the electromechanical surgical instrument when said adapter housing assembly is operably coupled thereto and apply axial firing motions to said surgical end effector while said surgical end effector is in said desired articulated position; characterised by a control system comprising means for monitoring strain experienced by said articulation actuator assembly during an application of axial firing motions to said surgical end effector and communicating a signal corresponding to a magnitude of said strain to a control circuit for the source of rotary articulation motions in the electromechanical surgical instrument to cause the source of rotary articulation motions to apply additional rotary articulation motions to said articulation actuator assembly required to maintain said surgical end effector in said desired articulated position during said application of axial firing motions to said surgical end effector. an adapter housing assembly configured to be operably coupled to the electromechanical surgical instrument; a shaft assembly defining a longitudinal axis between a proximal end and a distal end thereof, said proximal end operably coupled to said adapter housing assembly; a surgical end effector operably coupled to said distal end of said shaft assembly for selective articulation relative to said shaft assembly; an articulation actuator assembly configured to operably interface with a source of rotary articulation motions in the electromechanical surgical instrument when said adapter housing assembly is operably coupled thereto to apply axial articulation motions to said surgical end effector to move said surgical end effector into a desired articulated position; and a firing member assembly configured to operably interface with a source of rotary firing motions in the electromechanical surgical instrument when said adapter housing assembly is operably coupled thereto and apply axial firing motions to said surgical end effector while said surgical end effector is in said desired articulated position; characterised by a control system comprising means for monitoring strain experienced by said articulation actuator assembly during an application of axial firing motions to said surgical end effector and communicating a signal corresponding to a magnitude of said strain to a control circuit for the source of rotary articulation motions in the electromechanical surgical instrument to cause the source of rotary articulation motions to apply additional rotary articulation motions to said articulation actuator assembly required to maintain said surgical end effector in said desired articulated position during said application of axial firing motions to said surgical end effector.