1) During World War 1, soldiers experiencing mental trauma from the horrors of war without physical wounds were diagnosed with "shell shock". Symptoms included fatigue, irritability, and reliving traumatic experiences. 2) "Shell shock" was initially believed to be caused by physical damage from shell explosions but is now understood to be psychological trauma. Over 80,000 British soldiers alone were affected. 3) The public came to distrust their governments due to the immense human costs of the war and growing disillusionment with why the war was fought.