Which statement about the roles of defensive control measures is true?

The statement regarding defensive control measures that emphasizes their role in helping to determine the main battle area and task assignments is accurate because defensive control measures are essential planning tools used by military units to establish clear parameters for defense operations. These measures are put in place prior to engagement, allowing commanders to designate sectors of fire, define areas for maneuver, allocate resources, and assign specific roles and responsibilities to their units.

By clearly establishing the main battle area, leaders can ensure that all personnel are aware of their positions, tasks, and how they fit into the overall defensive strategy. This proactively enhances operational effectiveness, situational awareness, and coordination, which are vital in defensive operations to counter enemy advances efficiently.

In contrast, the other statements suggest a more reactive or inflexible approach, which does not align with the proactive planning that is essential in military strategy. Defensive control measures are intended to be part of the planning process rather than solely established after an attack, reactive strategies are broader in nature and not limited to defensive measures, and while flexibility is important, it should be applied within an established framework rather than resulting in constant change that could lead to confusion.