Combat stress reaction is a medical problem that happens to some soldiers because of the trauma of war.  In the past, it was called battle shock, war neurosis, or battle fatigue.  It causes both mental and physical problems.  It is similar to acute stress disorder, and can often become post-traumatic stress disorder.

Combat stress reaction does not affect everyone equally.  Sometimes it causes soldiers to be very unhappy.  Sometimes it causes soldiers severe disability.

The acute (early) stage of combat stress reaction is the best time to keep things from getting worse.  Since World War I, soldiers in early stages of combat stress reaction have usually been treated on the front lines - close to where combat is happening.

Symptoms 

Combat stress reaction can have many different symptoms.  These symptoms can affect the soldier's body (physical symptoms), feelings (emotional symptoms), and behaviors (behavioral symptoms).  Depending on how bad these symptoms are, combat stress reactions are labeled from mild (not too bad) to severe (very bad).

Physical Symptoms

Mild Symptoms 
Mild physical symptoms may include:
 Feeling tired  
 Feeling jumpy  
 Sweating  
 Having trouble sleeping  
 Fast heartbeat  
 Feeling dizzy  
 Feeling nauseous or throwing up  
 Having diarrhea  
 Urinating a lot  
 Not reacting as quickly as usual to things  
 Dry mouth  
 Tight muscles  
These symptoms may not cause safety problems, or keep the soldier from working.  However, if the soldier does not get help, the symptoms can become severe.

Severe Symptoms 

Severe symptoms may include:  
 Being unable to sit or stand still  
 Being startled very easily  
 Shaking or trembling  
 Weakness  
 Paralysis  
 Trouble hearing  
 Feeling exhausted  
 Being unable to move  
 Staring straight ahead without looking at anything (this is sometimes called "the thousand-yard stare")  
 Palpitations (pounding heart)  
 Hyperventilation (breathing too fast)  
 Feeling unable to speak  
 Being unable to sleep

Emotional Symptoms 
Emotional symptoms may include:
 Feeling anxious
 Having trouble concentrating or focusing on something
 Having nightmares
 Not feeling confident
 Feeling angry
 Feeling stressed or very upset over small things

Behavioral Symptoms 
Behavioral symptoms may include:
 Not being able to make decisions
 Not paying attention well
 Not caring about things
 Being very alert
 Not feeling motivated (not wanting to do anything)
 Aggressive behavior
 Crying
 Being unable to relax

History 

Sigmund Freud studied the effects of "war neurosis."  He believed that without too much stress, people can balance impulses (what they want to do) and prohibitions (what they know they should not do).  However, he thought that traumatic stress can cause powerful impulses that a person can no longer control.  In combat situations, he thought this could cause soldiers to run away, or to blindly attack.  He believed that soldiers would try to stop these impulses, which would lead to emotional symptoms and even loss of physical abilities.

World War I 
During World War I, combat stress reaction was called "shell shock."  By early 1916 (just halfway through the war), the number of British soldiers with "shell shock" was huge.  Few of these soldiers returned to battle.  About 30-40% of shell-shocked soldiers sent to hospitals in France returned to battle.  Only about 4-5% of soldiers sent to hospitals in the United Kingdom returned.

Because of this, new units were created.  They were called "Not Yet Diagnosed, Nervous Centers."  These centers did not use terms like "war neurosis" or "shell shock."  They used a new treatment model called "PIE" to treat soldiers with combat stress reaction.  "PIE" stood for "Proximity, Immediacy, and Expectancy":
 Proximity meant that soldiers with combat stress reaction should be treated close to the front line (close to where combat was happening).  
 Immediacy meant that these soldiers should be treated right away - not just after soldiers who were physically hurt were treated. 
 Expectancy meant that each soldier knew he was expected to return to combat.  
The PIE treatment model was developed by Thomas W. Salmon.  After "PIE" treatment was started, about 80% of soldiers treated at the "Not Yet Diagnosed, Nervous Centers" returned to combat.  (However, some of these soldiers were not able to do a good job when they returned to combat.)

World War II 
British forces did not use the PIE principles during World War II.  Instead, they sent soldiers with combat stress reaction to psychiatric hospitals.

The United States military did not expect their soldiers to have combat stress reactions when they entered the war.  They tested soldiers when they were enlisting (being signed up for military duty).  They believed that this testing would show which people were 'psychologically weak,' and that these people would not be allowed to go to war.  However, because combat stress reaction is not caused by weakness, this did not work, and many American soldiers had combat stress reactions.

To treat these soldiers, Captain Frederick Hanson began to use the PIE principles again.  He said that 70% of the 494 patients he treated returned to duty after 48 hours of PIE treatment.  General Omar Bradley decided to call combat stress reaction "exhaustion" and also decided to give "exhausted" soldiers seven days of rest.

The main goal of PIE was to return "exhausted" soldiers to combat, not to treat the trauma causing the disorder.  Because of this, many of the soldiers who returned to duty - possibly as many as 70% - returned in non-combat positions.

The Korean War 
During the Korean War, the United States started using the PIE principles within the first 8 weeks of the war.  Reports show that 65-75% of soldiers with combat stress reactions returned to duty.  However, only 44% were able to do their jobs at an average level or better.

The Vietnam War 
At the start of the Vietnam War, the United States military had effective psychiatric services in place within 8 weeks of the start of the war.  Treatments were based on the PIE principles.  Special mobile psychiatric units - soldiers who could give PIE treatment in different places - were created.

During the war, not many cases of combat stress reaction were reported.  Because of this, many people thought that combat stress reactions would no longer play a large part in warfare.

However, after soldiers returned home, many had problems with combat stress reaction.  Alienation lead to substance abuse, which hid combat stress reactions that had never been treated.  If the rates of post-traumatic stress disorder in Vietnam veterans are correct, the PIE principles did not prevent an epidemic of psychiatric disorders.

The First Gulf War 
The United States military went into this war expecting high numbers of psychological causalities.  The treatment included traditional psychiatry, as well as attention to family issues.  Because this war moved so fast, diagnosing soldiers with combat stress reaction was difficult.

Some commanders used combat stress reaction as an excuse to keep soldiers from returning or kick them out of the military.  This eventually added to the stigma attached to mental health problems in the military.

Treatment and Diagnosis Today 

Today, the United States Army uses the acronym BICEPS, which stands for brevity, immediacy, contact, expectancy, proximity, and simplicity:
 Brevity is a short period of rest.  Many soldiers return to duty after this brief rest.  More seriously affected patients are referred to the next level.  
 Immediacy means that treatment should start as soon as symptoms appear.  
 Contact means that the soldier should be able to see members of his or her unit while getting treatment.  This can help the soldier keep feeling like a soldier and a member of the unit, instead of feeling like a patient.  
 Expectancy means soldiers should be told their reaction to stress is normal, and that they are expected back with their unit.  
 Proximity (closeness) means that soldiers should be treated close to their unit, but away from patients who are physically hurt (unless nothing else is possible).  
 Simplicity means treatment should involve simple ways of improving soldiers' self-confidence and physical health. 

Today's treatment also includes the "5 R's": 
 Reassure normality (reassure soldiers that their reactions to stress are normal)
 Rest
 Replenish bodily needs (make sure soldiers'  bodies are getting what they need, like enough food and drink)
 Restore confidence
 Retain (keep) contact with fellow soldiers and unit  
Today, soldiers are treated for their response to combat stress, not like they have emotional problems.

References

Conflicts
Mental illnesses