A surgical instrument including a shaft, an end effector movable relative to the shaft, a locking mechanism configured to engage the shaft and/or end effector to fix the relative relationship between the shaft and end effector, and a closure system configured to close the end effector and engage the locking mechanism to prevent it from becoming unlocked. The instrument can further include a firing drive comprising a trigger, a firing member, and a pawl, where the pawl is rotatable between a first position in which the pawl is disengaged from the firing member and a second position in which the trigger can advance the pawl and firing member toward the end effector. The instrument can also include a reel, a band, where the band can be wound around the reel to retract the firing member, and a return mechanism for selectively engaging the trigger with the firing member and the reel.
