text: Glossary
  restrictive fire line
  A specific boundary established between converging, friendly surface forces that prohibits fires or their
  effects from crossing. (JP 3-09)
  *retain
  A tactical mission task in which a unit prevents enemy occupation or use of terrain.
  retirement
  When a force out of contact moves away from the enemy. (ADP 3-90)
  retrograde
  (Army) A type of defensive operation that involves organized movement away from the enemy.
  (ADP 3-90)
  *retrograde movement
  Any movement to the rear or away from the enemy.
  *route
  The prescribed course to be traveled from a point of origin to a destination.
  *route reconnaissance
  A form of reconnaissance operation to obtain detailed information of a specified route and all terrain
  from which the enemy could influence movement along that route.
  screen
  A type of security operation that primarily provides early warning to the protected force. (ADP 3-90)
  *search and attack
  A variation of a movement to contact where a friendly force conducts coordinated attacks to defeat a
  distributed enemy force.
  sector
  An operational area assigned to a unit in the defense that has rear and lateral boundaries with
  interlocking fires. (FM 3-0)
  *sector of fire
  That area assigned to a unit or weapon system in which it will engage the enemy according to the
  established engagement priorities.
  *secure
  A tactical mission task in which a unit prevents the enemy from damaging or destroying a force,
  facility, or geographical location.
  security
  Measures taken by a military unit, activity, or installation to protect itself against all acts designed to,
  or which may, impair its effectiveness. (JP 3-10)
  security area
  That area occupied by a unit’s security elements and includes the areas of influence of those security
  elements. (ADP 3-90)
  *security objective
  The most important entity to protect during that specific security effort.
  security operations
  Those operations performed by commanders to provide early and accurate warning of enemy
  operations, to provide the forces being protected with time and maneuver space within which to react
  to the enemy, and to develop the situation to allow commanders to effectively use their protected
  forces. (ADP 3-90)