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Common Tactical Concepts and Echelons 31 July 2019 ADP 3-90 2-17 UNCOMMITTED FORCES 2-78. An uncommitted force is a force that is not in contact with an enemy and is not already deployed on a specific mission or course of action. Commanders use uncommitted forces to exploit success or avoid failure. Echelon reserves are examples of uncommitted forces. WEIGHTING THE DECISIVE OPERATION OR MAIN EFFORT 2-79. The decisive operation is the operation that directly accomplishes the mission (ADP 3-0). Weighting the decisive operation or the main effort is a basic tactical concept closely associated with the mass and maneuver principles of war. The purpose for weighting the decisive operation or main effort is to concentrate the effects of combat power at the most advantageous place and time. A unit commander assumes risk in some areas to provide the resources required to mass combat power at a few key locations to support the unit’s decisive operation or main effort. FORMS OF MANEUVER AND FORMS OF THE DEFENSE 2-80. Leaders use the forms of maneuver and the forms of defense to elaborate COAs and schemes of maneuver. The forms describe the arrangement of friendly forces in relationship to the enemy. Understanding the simultaneity of decisive action is a key component of understanding the use of the forms of maneuver and defense. In operations where the preponderance of activities is offensive, there are units using a form of the defense. Similarly, in operations characterized by defensive activities, there are units using a form of maneuver. An example of this would be in a mobile defense where a static force conducts a defense of a linear obstacle while the striking force executes an envelopment. 2-81. Forms of maneuver are distinct tactical combinations of fire and movement with a unique set of doctrinal characteristics that differ primarily in the relationship between the maneuvering force and the enemy. The Army has five forms of maneuver—envelopment, frontal assault, infiltration, penetration, and turning movement. Combined arms organizations accomplish their missions by identifying when and where to execute these forms of maneuver. Commanders generally choose one form on which to build a COA. A higher echelon commander rarely specifies the specific form of maneuver a subordinate executes. However, that higher echelon commander’s intent and guidance, along with the mission and any implied tasks, may impose constraints such as time, security, and direction of attack that narrow the forms of maneuver to one alternative. Additionally, the AO’s characteristics and the enemy force’s dispositions help commanders determine the form of maneuver. A single operation may contain several forms of maneuver. (See FM 3-90-1 for a discussion of these forms of maneuver.) 2-82. There are three forms of the defense—perimeter defense, defense of a linear obstacle, and reverse slope defense. Commanders address each form of the defense differently when planning and executing their defense. When required to expand on a type of defensive operation, they apply a form of defense. ECHELONS 2-83. Army echelons have capabilities to perform different functions. These functions vary with the type of unit, the organization of the theater or joint operations area, the nature of the conflict, and the number and types of friendly forces committed to the effort. The echelons range from the fire team or crew, through the squad, section, platoon, company, battalion, and brigade to the division and corps. 2-84. At each echelon, a commander or leader task-organizes available capabilities to accomplish the mission. The purpose of task organization is to maximize different subordinate abilities to generate a combined arms effect consistent with the concept of operations. Commanders and staffs work to ensure the distribution of capabilities to the appropriate components of the force to weight the decisive operation and main effort. Command and support relationships describe the relationships between units within and supporting an echelon. (See ADP 5-0 for a discussion of these relationships.)