A surgical device comprising: a handle assembly including: a power source ; at least one motor coupled to the power source; and a controller configured to control the motor; an adapter assembly configured to selectively couple to the handle assembly, the adapter assembly including a strain gauge ; a reload configured to selectively couple to a distal portion of the adapter assembly, the reload including: a plurality of staples ("S"); an annular staple pusher for ejecting the plurality of staples; and an anvil assembly selectively couplable to the distal portion of the adapter assembly, the anvil assembly being movable relative to the reload; wherein: the strain gauge is configured to measure a strain caused by compression and stapling of tissue between the reload and the anvil assembly; and the controller is configured to control the motor to move the annular staple pusher based on the measured strain, the controller being configured to compare the measured strain to a maximum strain caused by a maximum stapling force during movement of the annular staple pusher and to stop the motor in response to the measured strain exceeding the maximum strain, characterized in that the controller is further configured to compare the measured strain to a minimum strain caused by a minimum stapling force during movement of the annular staple pusher to determine the presence of the plurality of staples ("S"), wherein a measured strain lower than the minimum strain is indicative that the plurality of staples is not present. a handle assembly including: a power source ; at least one motor coupled to the power source; and a controller configured to control the motor; a power source ; at least one motor coupled to the power source; and a controller configured to control the motor; an adapter assembly configured to selectively couple to the handle assembly, the adapter assembly including a strain gauge ; a reload configured to selectively couple to a distal portion of the adapter assembly, the reload including: a plurality of staples ("S"); an annular staple pusher for ejecting the plurality of staples; and a plurality of staples ("S"); an annular staple pusher for ejecting the plurality of staples; and an anvil assembly selectively couplable to the distal portion of the adapter assembly, the anvil assembly being movable relative to the reload; the strain gauge is configured to measure a strain caused by compression and stapling of tissue between the reload and the anvil assembly; and the controller is configured to control the motor to move the annular staple pusher based on the measured strain, the controller being configured to compare the measured strain to a maximum strain caused by a maximum stapling force during movement of the annular staple pusher and to stop the motor in response to the measured strain exceeding the maximum strain, characterized in that the controller is further configured to compare the measured strain to a minimum strain caused by a minimum stapling force during movement of the annular staple pusher to determine the presence of the plurality of staples ("S"), wherein a measured strain lower than the minimum strain is indicative that the plurality of staples is not present. <EOS>