A surgical instrument comprising: an elongate shaft assembly defining a shaft axis (SA-SA); a surgical end effector operably coupled to said elongate shaft assembly by an articulation joint such that said surgical end effector is selectively articulatable relative to said elongate shaft assembly about an articulation axis that is transverse to said shaft axis; a longitudinally movable flexible firing beam configured to flexibly traverse said articulation joint and being selectively axially movable from a starting position to an ending position within said surgical end effector; a proximal support link comprising an elongate proximal body and configured to laterally support proximal lateral side portions of said flexible firing beam traversing said articulation joint; a distal support link comprising an elongate distal body and configured to laterally support corresponding distal lateral side portions of said flexible firing beam traversing said articulation joint; further comprising a middle support member movably coupled to said elongate shaft assembly and a portion of said surgical end effector, said middle support member comprising a middle body portion including a proximal end and a distal end and a firing beam slot extending therebetween that is configured to movably support each lateral side of a portion of said flexible firing beam traversing said articulation joint; wherein said elongate proximal body is located proximal to said middle support member and said elongate distal body is located distal to said middle support member, wherein said proximal support link movably interfaces with said proximal end of said middle support member, and wherein said distal support link movably interfaces with said distal end of said middle support member; wherein the middle support member is pivotally coupled to the portion of the surgical end effector for pivotal travel relative thereto about a pivot axis and characterized in that the middle support member is coupled to the elongate shaft assembly for pivotal and axial travel relative thereto. an elongate shaft assembly defining a shaft axis (SA-SA); a surgical end effector operably coupled to said elongate shaft assembly by an articulation joint such that said surgical end effector is selectively articulatable relative to said elongate shaft assembly about an articulation axis that is transverse to said shaft axis; a longitudinally movable flexible firing beam configured to flexibly traverse said articulation joint and being selectively axially movable from a starting position to an ending position within said surgical end effector; a proximal support link comprising an elongate proximal body and configured to laterally support proximal lateral side portions of said flexible firing beam traversing said articulation joint; a distal support link comprising an elongate distal body and configured to laterally support corresponding distal lateral side portions of said flexible firing beam traversing said articulation joint; further comprising a middle support member movably coupled to said elongate shaft assembly and a portion of said surgical end effector, said middle support member comprising a middle body portion including a proximal end and a distal end and a firing beam slot extending therebetween that is configured to movably support each lateral side of a portion of said flexible firing beam traversing said articulation joint; wherein said elongate proximal body is located proximal to said middle support member and said elongate distal body is located distal to said middle support member, wherein said proximal support link movably interfaces with said proximal end of said middle support member, and wherein said distal support link movably interfaces with said distal end of said middle support member; wherein the middle support member is pivotally coupled to the portion of the surgical end effector for pivotal travel relative thereto about a pivot axis and characterized in that the middle support member is coupled to the elongate shaft assembly for pivotal and axial travel relative thereto.