A surgical instrument comprising: (a) an end effector, wherein the end effector comprises: (i) a first jaw, (ii) a second jaw pivotably coupled with the first jaw, wherein the second jaw is operable to move between an open position and a closed position, (iii) a knife configured to actuate between a pre-fired position and a fired position, and (iv) an electrode assembly (213, 215) configured to apply RF energy to tissue; (b) a handle assembly, wherein the handle assembly comprises: (i) a housing associated with the first jaw, (ii) an arm associated with the second jaw, wherein the arm is configured to pivot the second jaw between the open position and the closed position; and (c) a knife drive assembly comprising: (i) an input assembly, (ii) an output assembly coupled with the knife, and (iii) a compound pulley assembly rotatably disposed within the housing, wherein the compound pulley assembly comprises: a pair of pulley wheels rotatably coupled with the housing, wherein each pulley wheel comprises an input track and an output track, an input cable extending between the input track of each pulley wheel in the pair of pulley wheels, wherein the input cable is fixed to a sliding body of the input assembly, and an output cable extending between the output track of each pulley wheel in the pair of pulley wheels, wherein the output cable is fixed to the output assembly, wherein the input assembly is configured to drive the input cable a first proximal distance to in order to rotate the pair of pulley wheels in a first angular direction, thereby driving the output cable a first distal distance to actuate the knife from the pre-fired position toward the fired position, characterised in that the first distal distance is greater than the first proximal distance. (a) an end effector, wherein the end effector comprises: (i) a first jaw, (ii) a second jaw pivotably coupled with the first jaw, wherein the second jaw is operable to move between an open position and a closed position, (iii) a knife configured to actuate between a pre-fired position and a fired position, and (iv) an electrode assembly (213, 215) configured to apply RF energy to tissue; (i) a first jaw, (ii) a second jaw pivotably coupled with the first jaw, wherein the second jaw is operable to move between an open position and a closed position, (iii) a knife configured to actuate between a pre-fired position and a fired position, and (iv) an electrode assembly (213, 215) configured to apply RF energy to tissue; (b) a handle assembly, wherein the handle assembly comprises: (i) a housing associated with the first jaw, (ii) an arm associated with the second jaw, wherein the arm is configured to pivot the second jaw between the open position and the closed position; and (i) a housing associated with the first jaw, (ii) an arm associated with the second jaw, wherein the arm is configured to pivot the second jaw between the open position and the closed position; and (c) a knife drive assembly comprising: (i) an input assembly, (ii) an output assembly coupled with the knife, and (iii) a compound pulley assembly rotatably disposed within the housing, wherein the compound pulley assembly comprises: a pair of pulley wheels rotatably coupled with the housing, wherein each pulley wheel comprises an input track and an output track, an input cable extending between the input track of each pulley wheel in the pair of pulley wheels, wherein the input cable is fixed to a sliding body of the input assembly, and an output cable extending between the output track of each pulley wheel in the pair of pulley wheels, wherein the output cable is fixed to the output assembly, (i) an input assembly, (ii) an output assembly coupled with the knife, and (iii) a compound pulley assembly rotatably disposed within the housing, wherein the compound pulley assembly comprises: a pair of pulley wheels rotatably coupled with the housing, wherein each pulley wheel comprises an input track and an output track, an input cable extending between the input track of each pulley wheel in the pair of pulley wheels, wherein the input cable is fixed to a sliding body of the input assembly, and an output cable extending between the output track of each pulley wheel in the pair of pulley wheels, wherein the output cable is fixed to the output assembly, a pair of pulley wheels rotatably coupled with the housing, wherein each pulley wheel comprises an input track and an output track, an input cable extending between the input track of each pulley wheel in the pair of pulley wheels, wherein the input cable is fixed to a sliding body of the input assembly, and an output cable extending between the output track of each pulley wheel in the pair of pulley wheels, wherein the output cable is fixed to the output assembly, wherein the input assembly is configured to drive the input cable a first proximal distance to in order to rotate the pair of pulley wheels in a first angular direction, thereby driving the output cable a first distal distance to actuate the knife from the pre-fired position toward the fired position, characterised in that the first distal distance is greater than the first proximal distance.