A surgical stapling instrument comprising an elongate shaft assembly that defines a shaft axis and includes a surgical end effector that is operably coupled thereto by an articulation joint. The surgical instrument includes a longitudinally movable flexible firing beam that is configured to flexibly traverse the articulation joint and be selectively axially movable from a starting position to an ending position. A middle support member is movably coupled to the elongate shaft assembly and a portion of the surgical end effector. A proximal support link is located proximal to the middle support member and is configured to provide lateral support to a proximal portion of the flexible firing beam traversing the articulation joint. A distal support link is located distal to the middle support member and is configured to provide lateral support to a distal portion of the flexible support beam traversing the articulation joint.