Which of the following defensive tasks are NOT assigned to OPFOR elements at the battalion level and below?

The task that is not assigned to OPFOR elements at the battalion level and below is conducting a division-level counterattack. This is primarily because a division-level counterattack is a large-scale operation that involves coordination and control of multiple battalion and brigade-level assets, which supersedes the operational capabilities of battalion-level and below forces. Such strategic maneuvers typically require the involvement of higher command echelons, such as a division headquarters, to effectively mobilize and direct the necessary resources and support units required for such an extensive operation.

In contrast, defending a simple battle position, acting as a deception force, and acting as a security force are tasks well within the capabilities and assignment of smaller units like battalions or below. These tasks focus on localized defensive operations, tactical deception, and security measures that can be executed at a lower command level without needing the expansive coordination involved in division-level maneuvers.