Stapling assembly comprising a retraction drive

A surgical stapling system, comprising:

• a housing attachable to a motor drive system;
• a shaft extending distally from the housing, wherein the shaft defines a longitudinal axis;
• an end effector movable between an open configuration and a closed configuration, the end effector comprising:
• a cartridge jaw comprising a replaceable staple cartridge, wherein the staple cartridge comprises staples removably stored therein;
• and
• an anvil jaw;
• and
• a motor-driven firing drive, comprising:
• a firing member pushed distally from a proximal position to a distal fully-fired position during a firing stroke to eject the staples from the staple cartridge in response to a motor-driven input, the firing member comprising:
• a central portion movable within the end effector;
• an anvil jaw-engaging cam extending from the central portion that engages the anvil jaw during the firing stroke;
• a cartridge jaw-engaging cam extending from the central portion that engages the cartridge jaw during the firing stroke, wherein the anvil jaw-engaging cam and the cartridge jaw-engaging cam co-operatively hold the cartridge jaw and the anvil jaw in compression against patient tissue captured intermediate the cartridge jaw and the anvil jaw during the firing stroke;
• and
• a rotatable actuator knob extending proximally from the housing, wherein the rotatable actuator knob is selectively rotatable about a longitudinal drive axis to retract the firing member proximally.