Combat and Operational Stress Reactions

Combat and operational stress reactions (COSRs) are defined as “physical, emotional, cognitive, or behavioral reactions, adverse consequences, or psychological injuries of service members who have been exposed to stressful or traumatic events in combat or military operations,” according to DoD Instruction 6490.05. COSRs can vary in severity depending on a variety of operational conditions, including intensity, duration, frequency of combat exposure, leadership, and unit morale, among others. COSRs, however, do not represent mental health disorders or medically diagnosable conditions and concerns.

The term “combat and operational stress reaction” is used to describe two different types of military stress reactions: acute stress reactions in the combat environment called combat stress reactions (CSRs), and reactions to more sustained military operational stressors, or operational stress reactions (OSRs).

CSRs occur in combat or preparation for combat. They are hard-wired survival responses that encompass physiological, behavioral, emotional, mental, and other changes in body processes. Life threatening situations trigger the autonomic nervous system, which is regulated by two opposing divisions – the sympathetic nervous system, responsible for arousal, and the parasympathetic nervous system, responsible for shutdown. The result is a continuum of automatic responses referred to as the ‘defense cascade,’ characterized by extreme (but relatively brief) highs or lows in physiological functions, such as awareness/arousal, behavioral, emotional, mental, speech, and sensorimotor. These changes are intense and cause moderate to severe impairment while they last, but their duration is only hours or, at most, a few days.

OSRs are changes in physical or mental functioning or behavior resulting from the experience or consequences of military operations other than combat.

Examples of combat and operational stressors include:

Combat Stressors

  • Personal injury
  • Killing of combatants
  • Witnessing the death of an individual
  • Death of another unit member
  • Injury resulting in the loss of a limb

Operational Stressors

  • Prolonged exposure to extreme geographic environments such as desert heat or arctic cold
  • Reduced quality of life and limited access to resources over extended periods
  • Prolonged separation from family and/or other significant support systems

The signs and symptoms of CSRs include restlessness, panic, irritability, rage, confusion, memory problems, fatigue, insomnia, palpitations, shortness of breath, and dissociation. Signs and symptoms of OSRs include irritability or depressed mood, persistent anxiety or restlessness, changes in appetite or energy, insomnia, concentration difficulties, muscular tension or tremor.


Because COSRs are expected responses to combat and military operations, the services maintain programs to improve service members’ ability to manage combat and operational stress. These types of programs are referred to as combat and operational stress control (COSC) programs. The primary objectives of COSC programs are to:

  • help service members recognize signs and symptoms of COSRs
  • prevent them through training to increase confidence and skills
  • decrease the impact of combat and operational stress with simple measures, such as reassurance, rest, and ensuring safety

Some examples of interventions targeting COSRs include iCOVER and Combat and Operational Stress First Aid (COSFA), a Navy psychological first aid toolkit.

If service members with COSRs do not respond to initial interventions, referral to a licensed mental health provider is recommended.

PHCoE’s Combat Stress Reactions: Tips for Providers offers an overview of the ‘defense cascade’ described above, examples of service members’ experiences, and tips for working with service members who may experience CSRs.