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Chapter 2 2-4 ADP 3-90 31 July 2019 DEFEAT MECHANISMS 2-11. A defeat mechanism is a method through which friendly forces accomplish their mission against enemy opposition (ADP 3-0). Tactical forces at all echelons use combinations of the four defeat mechanisms: destroy, dislocate, disintegrate, and isolate. There are also stability mechanisms used in the conduct of stability. (See ADP 3-0 for a discussion of both defeat and stability mechanisms.) BASIC TACTICAL CONCEPTS 2-12. Paragraphs 2-13 through 2-79 discuss the basic tactical concepts common to both the offense and defense. These concepts—along with the principles of joint operations, the mission variables, operational design, warfighting functions, running estimates, input from other commanders, and their own experience and judgment—allow commanders to articulate their concept of operations. AREA OF INFLUENCE 2-13. An area of influence is a geographical area wherein a commander is directly capable of influencing operations by maneuver or fire support systems normally under the commander’s command or control (JP 3-0). Understanding an area of influence helps commanders and staffs identify the broader effects of operations and branches to the current plan. Commanders collaborate to define AOs to match a unit’s area of influence. An AO that is too large for a unit to control provides an enemy force with maneuver space or depletes a commander’s combat power. If an area of influence differs in size from its assigned AO, commanders or appropriate staff officers—  Change the dispositions of available current systems to match the size of an area of influence and ensure coverage of key areas, installations, and systems.  Request additional assets.  Request boundary adjustments to reduce the size of an AO.  Communicate the increased risk and use economy of force measures.  Adjust a unit’s area of influence by phases to encompass an entire AO. AREA OF INTEREST 2-14. An area of interest is that area of concern to the commander, including the area of influence, areas adjacent thereto, and extending into enemy territory (JP 3-0). This area also includes areas occupied by enemy forces who could jeopardize the accomplishment of the mission. Typically, a commander’s area of interest is much larger than that commander’s AO. Depending on the type and scale of an operation, the size of an assigned area of interest varies. AREA OF OPERATIONS 2-15. 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). The joint force land component commander, Army Service component command commander, or Army forces commander assigns subordinates AOs. Those subordinates further assign AOs from their assigned AO, down to the battalion or company echelon based on the mission variables. A unit assigned an AO may not change control measures imposed by a higher echelon headquarters within its AO. However, it may establish additional Basic Tactical Concepts Area of influence Area of interest Area of operations Avenue of approach Combined arms Committed force Concept of operations Decisive engagement Defeat in detail Economy of force Encirclement Engagement area Flanks Forms of contact Local security Maneuver Meeting engagement Movement Mutual support Operation Operational framework Piecemeal commitment Reconstitution Reserve Rules of engagement Supporting distance Supporting range Tactical mobility Uncommitted forces Weight the decisive operation