A surgical cutting and stapling instrument is disclosed. The instrument includes an end effector and a handle. The end effector includes a channel, an anvil pivotally attached to the channel, a moveable cutting instrument for cutting an object positioned between the anvil and the channel, and a staple cartridge configured for removable receipt by the channel. The staple cartridge includes a sled that is engaged by the cutting instrument during a cutting stoke. The handle includes a motor for actuating the cutting instrument via a main drive shaft assembly. The instrument further includes a first interlock circuit for enabling initiation of motor operation based upon a position of the staple cartridge.