text: Environmental and Terrain Considerations for Fire Support
  suppressive fires for the final assault to the objective and beyond the limit of advance to stop enemy force
  retreat or reinforcement.
  NIGHT DEFENSIVE OPERATIONS
  D-132. The effective employment of FS is critical to the successful night defense. As with the offense,
  daylight planning and coordination considerations are used in addition to considerations for night defense,
  which include:
  * Use on-call fires to engage enemy forces as they attack or probe the defense.
  * Plan illumination fires although the appropriate supported commander is the approving authority
  for defensive illumination fires. This is to preclude accidental illumination of friendly activity such
  as patrols and engineer activities. When used, drop visible illumination above and behind attacking
  forces to silhouette them.
  * Adjust fires, especially FPFs, during daylight, if possible.
  * Use smoke to slow, confuse, and disorient attacking forces.
  * Plan FA delivered mines in coordination with the engineer to separate forces, disrupt formations,
  and plug gaps in the defense.
  * Plan permissive FS measures as close to friendly troops as possible; however, measures should be
  placed on positively identifiable terrain.
  * Plan restrictive measures, if required, on easily identifiable terrain to provide safety to friendly
  elements.
  SECTION VII – CONTINUOUS OPERATIONS
  D-133. Physiological aspects of continuous operations include those factors that degrade the Soldier's
  physical ability to function. Sleep loss and fatigue induced by night operations magnify stress. After 48 hours
  of sustained activity, loss of sleep becomes the most significant degrader of Soldier performance on the
  battlefield. As sleep loss begins to accumulate, both physical and mental effects are observed in varying
  degrees. Most of the following effects can occur after 24 hours without sleep:
  * Tasks may be omitted as a result of a momentary lapse into sleep (falling asleep with eyes open).
  * Vigilance decreases rapidly, resulting in missed critical signals.
  * Ability to focus on a task for more than a brief period decreases noticeably.
  * Memory becomes faulty, particularly short-term memory. This makes it difficult to learn new
  information, follow instructions, or remember recent decisions.
  * Response to events or instructions slows. One seems to be operating in a daze.
  * The ability to formulate and make sense from information becomes severely degraded. It takes
  longer to perform simple tasks such as plotting grid coordinates. Accuracy suffers.
  * The ability to reason logically is degraded, which may result in snap judgments.
  * Problems with communication arise. One has difficulty understanding or articulating even simple
  messages.
  * A wide range of mood changes, characterized by depression, anger, lack of patience, and euphoria,
  can occur.
  D-134. Sleep loss is cumulative over time. The number of hours needed to recover is directly related to the
  number of hours sleep was deprived. As a rule of thumb, a minimum of 6 hours rest is required for every 24
  hours without sleep. Fatigue is the result of excessive work and sleep loss. The latent effects of fatigue may
  linger for about 3 days following sleep deprivation of 48 hours or more.
  SECTION VIII – COLD WEATHER OPERATIONS
  D-135. Fire planning for cold weather operations is no different than that required for more temperate
  regions. However, the FS planner must consider that artillery weapon systems may have limited mobility in
  snow and ice that will also affect ammunition supply and increase to time to accomplish tasks.