ADP 3-90, page 91

Glossary 31 July 2019 ADP 3-90 Glossary-5 *corps An echelon of command and tactical formation that employs divisions, multi-functional brigades, and functional brigades to achieve objectives on land. countermobility operations (Army) Those combined arms activities that use or enhance the effects of natural and man-made obstacles to deny enemy freedom of movement and maneuver. (ATP 3-90.8) *cover (Army) A type of security operation done independent of the main body to protect them by fighting to gain time while preventing enemy ground observation of and direct fire against the main body. *crew A small military unit that consists of all personnel operating a particular system. decisive operation The operation that directly accomplishes the mission. (ADP 3-0) *decisive terrain Key terrain whose seizure and retention is mandatory for successful mission accomplishment. *decisive engagement An engagement in which a unit is considered fully committed and cannot maneuver or extricate itself. defeat To render a force incapable of achieving its objectives. (ADP 3-0) *defeat in detail Concentrating overwhelming combat power against separate parts of a force rather than defeating the entire force at once. defeat mechanism A method through which friendly forces accomplish their mission against enemy opposition. (ADP 3-0) defensive operation An operation to defeat an enemy attack, gain time, economize forces, and develop conditions favorable for offensive or stability operations. (ADP 3-0) *delay When a force under pressure trades space for time by slowing down the enemy’s momentum and inflicting maximum damage on enemy forces without becoming decisively engaged. *deliberate operation An operation in which the tactical situation allows the development and coordination of detailed plans, including multiple branches and sequels. *detachment A tactical element organized on either a temporary or permanent basis for special duties. *direction of attack A specific direction or assigned route a force uses and does not deviate from when attacking. *disengagement line A phase line located on identifiable terrain that, when crossed by the enemy, signals to defending elements that it is time to displace to their next position. *division An echelon of command and tactical formation that employs brigade combat teams, multi-functional brigades, and functional brigades to achieve objectives on land.