A surgical instrument can comprise a rotary input shaft and a surgical end effector that comprises a first jaw and a second jaw that is movable relative to the first jaw. The surgical instrument can further comprise a firing shaft that operably interfaces with the rotary input shaft. A firing member is movably supported in one of the first and second jaws. A closure member is in threaded engagement with the rotary input shaft such that rotation of the rotary input shaft in a first direction causes the closure member to move the second jaw to the closed position. The closure member remains in threaded engagement with the rotary input shaft to positively retain the second jaw in the closed position while continued rotation of the rotary input shaft in the first direction drives the firing member from a start position to an end position.
