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Chapter 4 4-2 ADP 3-90 31 July 2019 and cyberspace assets in addition to lethal systems to target enemy command and control systems and disrupt enemy forces in depth by isolating forward echelons from their higher echelon headquarters. FLEXIBILITY 4-7. Defensive operations require flexible plans that anticipate enemy actions and allocates resources accordingly. Commanders shift the main effort as required. They plan battle positions in depth and the use of reserves in spoiling attacks and counterattacks. MANEUVER 4-8. Maneuver allows a defending force to achieve and exploit a position of advantage over an enemy force. As described in paragraphs 1-23 through 1-32, even in the defense there are elements of the offense. The defending force seeks opportunities to maneuver against the attacking force. MASS AND CONCENTRATION 4-9. Defending forces seek to mass and concentrate effects against enemy forces. This action produces overwhelming combat power at specific locations to support their decisive operations. Defending forces can surrender ground to gain time for maneuver that allows them to mass and concentrate effects. 4-10. Commanders accept certain risk to mass effects at decisive points or for their main efforts. Concentrating forces increases the risk of large-scale losses from enemy fires and weapons of mass destruction. They mitigate this risk by using military deception and concealment to avoid detection of friendly troop concentrations by enemy intelligence, surveillance, and reconnaissance assets. 4-11. Commanders designate, retain, and when necessary reconstitute a reserve. They employ their reserve to exploit counterattack opportunities, regain local superiority, preserve the integrity of their defense, and prevent friendly culmination. They reconstitute their reserve from other forces when their reserve is committed. OPERATIONS IN DEPTH 4-12. Operations in depth is the simultaneous application of combat power throughout an area of operations. Commanders plan their operations in depth. They create conditions by disrupting enemy long-range fires, sustainment, and command and control. These disruptions weaken enemy forces and prevent any early enemy successes. Operations in depth prevent enemy forces from maintaining their tempo. In the defense, commanders establish a security area and the main battle area (MBA) with its associated FEBA. (See paragraphs 4-31 and 4-33 for more information about the FEBA and MBA respectively.) PREPARATION 4-13. Defending units prepare their AOs before attacking enemy forces arrive, or they establish the defense behind a force performing a security operation. Commanders employ forward and flank security forces to protect their defending forces from surprise and reduce the unknowns in any situation. Defending forces study the terrain, study enemy forces, and prepare engagement areas. They combine natural and man-made obstacles to canalize attacking forces into those engagement areas. Defending forces place information collection assets throughout their AOs to provide intelligence and early warning of enemy actions. They position combat multipliers, such as fires and sustainment assets, to support their defensive plans. Defending forces improve the survivability of their units by constructing field fortifications, using camouflage, and dispersing. Defending forces continue rehearsals and preparations until close combat begins. SECURITY 4-14. Commanders secure their forces through the performance of security, protection, information operations, and cyberspace and electronic warfare tasks. Security may include the provision of area security for civilians, infrastructure, and LOCs. Security operations prevent enemy intelligence, surveillance, and reconnaissance assets from determining friendly locations, strengths, and weaknesses. These operations also