ADP 3-90, page 80

Chapter 4 4-20 ADP 3-90 31 July 2019 offense, and they do not want to give an enemy force time to prepare for the defense. Additionally, the psychological shock on enemy soldiers will be greater if they suddenly find themselves defending on unfavorable terms. 4-124. There are two methods for transitioning to an offense. The first, and generally preferred method, is to attack using forces not previously committed to a defense. This method is preferred because defending units may still be decisively engaged, tired, or depleted. These attacking forces may come from the reserve or consist of reinforcements. Since these forces have not recently been actively involved in combat, they are more likely to—  Be at authorized strength levels.  Have a higher combat system operationally readiness rate.  Have leaders and Soldiers who are more likely to be rested and more capable of prolonged, continuous operations.  Have a complete basic load of supplies.  Have the time and energy to plan and prepare to conduct the offensive operations.  Be able to maneuver out of physical contact with an enemy force. 4-125. The second method is to perform a type of offensive operation using currently defending forces. This method generally has the advantage of being more rapidly executed and thus more likely to catch an enemy force by surprise. Speed of execution in this method results from not having to conduct an approach or tactical road march from reserve assembly areas or, in the case of reinforcements, move from other AOs and reception, staging, onward movement, and integration locations. Speed also results from not having to conduct a forward passage of lines and performing the liaison necessary to establish a common operational picture that includes knowledge of the enemy force’s patterns of operation. 4-126. If units in contact participate in an attack, commanders must retain sufficient forces in contact to fix enemy forces. Commanders concentrate an attack by reinforcing select subordinate units so they can execute the attack and, if necessary, maintain the existing defense. Commanders can also adjust the defensive boundaries of subordinate units so entire units can withdraw and concentrate for an attack. TRANSITION TO STABILITY 4-127. A force may transition from defensive operations to stability operations. This generally occurs if the force reaches and establishes a defense along a LOA. Then, there may be a negotiated end to hostilities from which the force transitions to stability. While improving its defensive preparations, the force may begin to increase the amount of resources dedicated to stability.