A surgical instrument comprising: (a) a body assembly, wherein the body assembly comprises a proximal end and a distal end; (b) a shaft assembly, wherein the shaft assembly extends distally from the distal end of the body assembly, wherein the shaft assembly comprises a proximal end and a distal end; (c) a stapling assembly, wherein the stapling assembly is disposed at the distal end of the shaft assembly, wherein the stapling assembly is operable to drive a plurality of staples into tissue, wherein the stapling assembly comprises: (i) a trocar, wherein the trocar is configured to selectively move between a distal position to a proximal position within the shaft assembly, and (ii) an anvil, wherein the anvil is selectively coupleable with the trocar, wherein the anvil is configured to move between the distal position and the proximal position when coupled with the trocar; (d) a firing assembly, wherein the firing assembly is coupled with the stapling assembly, wherein the firing assembly is configured to drive movement of the stapling assembly; wherein the instrument further comprises a battery pack, wherein the battery pack is configured to provide power to the firing assembly, wherein the battery pack is selectively insertable into and removable from the body assembly, characterised in that the body assembly comprises a lockout assembly (5140, 5142, 5132, 5160) configured to limit movement of the trocar when the battery pack is not inserted within the body assembly. (a) a body assembly, wherein the body assembly comprises a proximal end and a distal end; (b) a shaft assembly, wherein the shaft assembly extends distally from the distal end of the body assembly, wherein the shaft assembly comprises a proximal end and a distal end; (c) a stapling assembly, wherein the stapling assembly is disposed at the distal end of the shaft assembly, wherein the stapling assembly is operable to drive a plurality of staples into tissue, wherein the stapling assembly comprises: (i) a trocar, wherein the trocar is configured to selectively move between a distal position to a proximal position within the shaft assembly, and (ii) an anvil, wherein the anvil is selectively coupleable with the trocar, wherein the anvil is configured to move between the distal position and the proximal position when coupled with the trocar; (i) a trocar, wherein the trocar is configured to selectively move between a distal position to a proximal position within the shaft assembly, and (ii) an anvil, wherein the anvil is selectively coupleable with the trocar, wherein the anvil is configured to move between the distal position and the proximal position when coupled with the trocar; (d) a firing assembly, wherein the firing assembly is coupled with the stapling assembly, wherein the firing assembly is configured to drive movement of the stapling assembly; wherein the instrument further comprises a battery pack, wherein the battery pack is configured to provide power to the firing assembly, wherein the battery pack is selectively insertable into and removable from the body assembly, characterised in that the body assembly comprises a lockout assembly (5140, 5142, 5132, 5160) configured to limit movement of the trocar when the battery pack is not inserted within the body assembly.