The references establish the system used to publish all training standards, provide policy, and assign training responsibilities, especially as applied to the Systems Approach to Training (SAT). ITSs establish the training requirements for all Marines in the same occupational field (OccFld), Military Occupational Specialty (MOS), or billet. They provide a foundation upon which unit commanders and school directors build training packages for individual Marines as part of unit training plans or formal courses of instruction. ITSs represent the skills that contribute to the unit mission as expressed in the Mission Performance Standards. Changes to doctrine or force structure or the introduction of new weapons or equipment may necessitate revision of this Order.