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.
Trench railways
Trench railways represented military adaptation of early 20th century railway technology to the problem of keeping soldiers supplied during the static trench warfare phase of World War I. The large concentrations of soldiers and artillery at the front lines required delivery of enormous quantities of food, ammunition and fortification construction materials where transport facilities had been destroyed. Reconstruction of conventional roads (at that time rarely surfaced) and railways was too slow, and fixed facilities were attractive targets for enemy artillery. Trench railways linked the front with standard gauge railway facilities beyond the range of enemy artillery. Empty cars often carried litters returning wounded from the front.