Combat stress reaction (CSR) is acute behavioral disorganization as a direct result of the trauma of war. Also known as "combat fatigue", "battle fatigue", or "battle neurosis", it has some overlap with the diagnosis of acute stress reaction used in civilian psychiatry. It is historically linked to shell shock and can sometimes precurse post-traumatic stress disorder. Combat stress reaction is an acute reaction that includes a range of behaviors resulting from the stress of battle that decrease the combatant's fighting efficiency. The most common symptoms are fatigue, slower reaction times, indecision, disconnection from one's surroundings, and the inability to prioritize. Combat stress reaction is generally short-term and should not be confused with acute stress disorder, post-traumatic stress disorder, or other long-term disorders attributable to combat stress, although any of these may commence as a combat stress reaction. The US Army uses the term/acronym COSR (Combat Stress Reaction) in official medical reports. This term can be applied to any stress reaction in the military unit environment. Many reactions look like symptoms of mental illness (such as panic, extreme anxiety, depression, and hallucinations), but they are only transient reactions to the traumatic stress of combat and the cumulative stresses of military operations. In World War I, shell shock was considered a psychiatric illness resulting from injury to the nerves during combat. The nature of trench warfare meant that about 10% of the fighting soldiers were killed (compared to 4.5% during World War II) and the total proportion of troops who became casualties (killed or wounded) was about 57%. Whether a person with shell-shock was considered "wounded" or "sick" depended on the circumstances. When faced with the phenomenon of a minority of soldiers mentally breaking down, there was an expectation that the root of this problem lay in character of the individual soldier, not because of what they experienced on the front lines during the war. The large proportion of World War I veterans in the European population meant that the symptoms were common to the culture. Signs and symptoms Combat stress reaction symptoms align with the symptoms also found in psychological trauma, which is closely related to post-traumatic stress disorder (PTSD). CSR differs from PTSD (among other things) in that a PTSD diagnosis requires a duration of symptoms over one month, which CSR does not. Fatigue-related symptoms The most common stress reactions include: The slowing of reaction time Slowness of thought Difficulty