A surgical instrument comprising: a tool drive portion configured for operable attachment to a portion of a robotic system for receiving control motions therefrom; an elongated shaft coupled to said tool drive portion; an axially movable control member operably supported within said elongated shaft and being axially movable in response to actuation motions applied thereto from said robotic system; and a disposable loading unit comprising: a housing coupled to said elongated shaft; a cartridge assembly including a staple cartridge supported by said housing; an axial drive assembly supported for selective axial travel through said cartridge assembly from a start position to an end position upon application of a rotary motion thereto; a motor supported within said housing and operably interfacing with said axial drive assembly to selectively apply said rotary motion thereto; and a power source axially movable within said housing from a disconnected position wherein said power source is disconnected from said motor to a first connected position wherein said power source provides power to said motor upon attachment to the control member, characterized in that: the surgical instrument further comprises a drive shaft assembly coupled to a proximal end of the axially movable control member, a rotary drive gear, a rotatable body portion coupled to the rotary drive gear, and a gear train in meshing engagement with the rotary drive gear and drive shaft assembly, such that rotation of the rotary drive gear results in the axial advancement of the axially movable control member. a tool drive portion configured for operable attachment to a portion of a robotic system for receiving control motions therefrom; an elongated shaft coupled to said tool drive portion; an axially movable control member operably supported within said elongated shaft and being axially movable in response to actuation motions applied thereto from said robotic system; and a disposable loading unit comprising: a housing coupled to said elongated shaft; a cartridge assembly including a staple cartridge supported by said housing; an axial drive assembly supported for selective axial travel through said cartridge assembly from a start position to an end position upon application of a rotary motion thereto; a motor supported within said housing and operably interfacing with said axial drive assembly to selectively apply said rotary motion thereto; and a power source axially movable within said housing from a disconnected position wherein said power source is disconnected from said motor to a first connected position wherein said power source provides power to said motor upon attachment to the control member, a housing coupled to said elongated shaft; a cartridge assembly including a staple cartridge supported by said housing; an axial drive assembly supported for selective axial travel through said cartridge assembly from a start position to an end position upon application of a rotary motion thereto; a motor supported within said housing and operably interfacing with said axial drive assembly to selectively apply said rotary motion thereto; and a power source axially movable within said housing from a disconnected position wherein said power source is disconnected from said motor to a first connected position wherein said power source provides power to said motor upon attachment to the control member, characterized in that: the surgical instrument further comprises a drive shaft assembly coupled to a proximal end of the axially movable control member, a rotary drive gear, a rotatable body portion coupled to the rotary drive gear, and a gear train in meshing engagement with the rotary drive gear and drive shaft assembly, such that rotation of the rotary drive gear results in the axial advancement of the axially movable control member.