text: Chapter 5
  5-87. As the division is either defeating or destroying an enemy and seizing terrain, it also ensures that
  activities in the division’s rear are synchronized and secured. The division’s rear, which encompasses both
  the support areas and the physical space between the BCT rear boundaries and the division rear boundaries,
  grows as a division conducts offensive operations and shrinks as the corps shifts its rear boundary forward.
  The rear typically has one or more support areas during sustained offensive operations. Divisions have a wide
  variety of tasks associated with their rear, including defeating bypassed enemy forces and performing
  minimum essential stability tasks, terrain management, lines of communication security, route clearance,
  movement control, and security. A large number of different units are located in the division’s rear (inside
  and outside of the support area), not all of which are under division control, but which support the division
  (and corps).
  5-88. In support areas, the focus is on maintaining and extending friendly operational reach to prevent
  friendly culmination. This requires anticipation by the staff and commander. While a division is planning
  72 to 96 hours out in terms of shaping operations, it generally plans even further out in terms of sustaining
  operations because of the physics associated with moving large amounts of supplies and distributing them.
  Generally, a MEB is responsible for the security of the support area, which allows sustainment units to focus
  on their primary mission. A division may have one or multiple support areas to avoid presenting a single
  lucrative target and to facilitate sustainment when the division is operating along multiple axes on a wide
  front, exceeding the MEB’s security capabilities. In this case, the division commander directs other units to
  provide additional security or accepts risk.