Final answer:
The "Sustainment" portion of an Operation Order in military science addresses the logistical support required to sustain the forces during the operation.
Step-by-step explanation:
In military science, the "Sustainment" portion of an Operation Order addresses the logistical support required to sustain the forces during the operation. It includes planning for resupply of ammunition, fuel, food, and medical support, as well as maintenance of equipment and transportation. This portion ensures that the necessary resources are available to sustain the mission and keep the forces operational.