ADP 3-90, page 77

The Defense 31 July 2019 ADP 3-90 4-17 Chemical, Biological, Radiological, and Nuclear Defense 4-103. Defending units are often in fixed positions and have an increased vulnerability to CBRN threats and hazards. Commanders specify the degree of acceptable risk and establish priorities for CBRN defense assets. 4-104. Units establish, train, rehearse, and exercise a CBRN defense plan to protect personnel and equipment from CBRN hazards. Mission-oriented protective posture (known as MOPP) analysis can be used as a tool to support—  Determining the appropriate protective posture, estimating unit and personnel effectiveness (for example, mission degradation).  Estimating additional logistic requirements (for example, water resupply and individual protective equipment replenishment).  Assessing and weighing the tradeoffs between agent exposures versus degraded performance (for example, wearing full CBRN protective equipment). Medical personnel continuously maintain and conduct comprehensive health surveillance (health, medical, occupational, and environmental health surveillance). Commanders ensure that their units can conduct operational and thorough decontamination of military personnel and equipment. Commanders are responsible for CBRN passive defense training to prepare their units to respond properly to CBRN threats. 4-105. Commanders integrate CBRN reconnaissance and surveillance into the overall information collection plan. Employment of CBRN reconnaissance and surveillance capabilities should not duplicate the efforts of conventional reconnaissance assets. 4-106. CBRN personnel contribute to the overall protection of units located in defensive positions. CBRN personnel perform CBRN vulnerability assessments including a threat assessment and vulnerability analysis, and they recommend vulnerability reduction measures for commanders to consider before and after units move into their defensive positions. These assessments provide a list of preventive measures that can range from the use of obscurants, reconnaissance, mission-oriented protective posture, and other aspects of CBRN defense. (For more information on CBRN vulnerability assessment, see ATP 3-11.36. For more information on CBRN protection, see ATP 3-11.32.) Physical Security and Antiterrorism 4-107. Enemy forces employ all means to attack defending maneuver elements, command and communications nodes, LOCs, sustainment sites, and civilian population centers in an attempt to disrupt the defense. Commanders pay attention to physical security and antiterrorism operations throughout a defense. This is especially true when a defending unit conducts noncontiguous operations. 4-108. The success of a unit defense may depend on protecting the support area from enemy attacks. Commanders must address the early detection and immediate destruction of enemy forces attempting to attack support areas. Enemy attacks in these areas against sustainment and other facilities can range in size from individual saboteurs to enemy airborne or air assault insertions targeted against key military and civilian facilities and capabilities. These enemy activities, especially at smaller unit levels, may even precede the onset of large-scale combat and be almost indistinguishable from terrorist acts. 4-109. Planners determine how military police elements supporting a defending unit will enhance unit physical security and antiterrorism capabilities by performing area security tasks inside and outside an echelon support area. Military police may defeat Level II threats against bases and base clusters located in an echelon support area. They will maintain contact with Level III threats until a tactical combat force can respond. (See ATP 3-91 for a discussion of the threat levels. See FM 3-90-2 for a discussion of security operations.) Conduct Population and Resource Control 4-110. Commanders plan for dislocated civilians and the effect that they have on the defense. Civil affairs units help commanders in planning population and resource control measures. A defending unit uses host-nation and international organizations as much as possible to minimize the effects of disaster or conflict on dislocated civilians and thereby avoid diverting unit resources to conduct stability operations.