This paper describes the development of the octopus biology inspired OctArm series of soft robot manipulators. Each OctArm is constructed using air muscle extensors with three control channels per section that provide two axis bending and extension. Within each section, mesh and plastic coupler constraints prevent extensor buckling. OctArm IV is comprised of four sections connected by endplates, providing twelve degrees of freedom. Performance of OctArm IV is characterized in a lab environment. Using only 4.13 bar of air pressure, the dexterous distal section provides 66% extension and 380° of rotation in less than .5 seconds. OctArm V has three sections and, using 8.27 bar of air pressure, the strong proximal section provides 890 N and 250 N of vertical and transverse load capacity, respectively. In addition to the in-lab testing, OctArm V underwent a series of field trials including open-air and in-water field tests. Outcomes of the trials, in which the manipulator demonstrated the ability for adaptive and novel manipulation in challenging environments, are described. OctArm VI is designed and constructed based on the in-lab performance, and the field testing of its predecessors. Implications for the deployment of soft robots in military environments are discussed.