Chances are that, if you read about wars and the effect it has on soldiers, you may have inadvertently seen the "Thousand Yard Stare". The first sign of Post-Traumatic Stress Disorder (PTSD) in many cases, it defined as "a vacant or unfocused gaze into the distance, seen as characteristic of a war-weary or traumatized soldier", by Oxford dictionaries. The origin of the phrase comes from Time magazine's publishing a painting titled "Marines Call It That 2,000 Yard Stare", made by World War II artist and correspondent Tom Lea, although it was not explicitly called that. The painting is a 1944 portrait of a Marine at the Battle of Peleliu in Palau (Pacific theater). About the real-life Marine who was his subject, Lea said:
He left the States 31 months ago. He was wounded in his first campaign. He has had tropical diseases. He half-sleeps at night and gouges Japs out of holes all day. Two-thirds of his company has been killed or wounded. He will return to attack this morning. How much can a human being endure?
Prolonged exposure to battle causes the thousand yard stare. You can imagine that it was quite common during the Second World War, Vietnam (and practically any war, to be quite honest). It need not be confined simply to war.
While we're on this topic, it should be clarified that the 1984 photo of Sharbat Gula (popularly coined as the "Afghan Girl"), who obtained international notability for a photo depicting her in a refugee camp in Pakistan after she was orphaned, is generally considered to not portray the stare. But it is still one of the most defining images of the 20th century.
