Trench warfare
Trench warfare occurred when a revolution in firepower was not matched by similar advances in mobility, resulting in a grueling form of warfare in which the defender held the advantage. On the Western Front in 1914–1918, both sides constructed elaborate trench, underground, and dugout systems opposing each other along a front, protected from assault by barbed wire, mines, camouflaged trapping pits, and other obstacles. The area between opposing trench lines (known as "no man's land") was fully exposed to artillery fire from both sides. Attacks, even if successful, often sustained severe casualties.
Male hysteria
World War I was the first instance in which a war neurosis and mental trauma was rampant and affected soldiers considerably. This could be attributed to the particular form of fighting – trench warfare – which was impersonal and constantly kept the soldier on edge for the next attack. Eric Leed writes that war neurosis was a result of the breakdown of the previously personal relationship of the soldier and his means of fighting. Rivers considered the idea that the traumatized men resorted to neurotic behavior because of a loss of their usual defense mechanism – physical hand-to-hand combat.