3-5. When integrating fires into their plan, each echelon must consider both the needs of their own commander, as well as their role in executing the plan of the echelons above them. Lower echelons will generally have more tactical information available to them and are therefore responsible for refining and executing their portion of the plan of the higher echelon to ensure that the intent of the higher commander is met. An example of this type of refinement is refinement of the location of a target from a general location to a specific location based on the subordinate commander’s understanding of the terrain and use of obstacles. To integrate fires with the other elements of combat power, planners must build an environment that is permissive for the use of fires capabilities. In the physical domains, this is accomplished primarily through the use of control measures to delineate responsibilities. A control measure is a means of regulating forces or warfighting functions (ADP 6-0). This delineation of responsibilities begins with the assignment of an AO. An area of operations is an operational area defined by a commander for land and maritime forces that should be large enough to accomplish their missions and protect their forces (JP 3-0). Unit responsibilities within their assigned AO include: