From shell shock to combat stress

What preceded the term shell shock, and when did battle fatigue become common?

Earlier periods described war exhaustion; shell shock emerged in the First World War, battle fatigue followed later, and modern language shifted toward combat stress and PTSD.

The terminology moves from shell shock through battle fatigue to combat stress and PTSD. The initial shell-shock label linked symptoms to artillery bombardment. In this account, First World War mass mobilization exposed a wider cross-section of people to combat and made individual moral-failure explanations harder to sustain. Earlier language included war exhaustion, with the Napoleonic period used as an example of recognizing that prolonged warfare depleted a soldier's capacity to cope. Troop rotation addressed that exhaustion even when its causes were understood differently.