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.
Tunnel warfare
The oldest known sources about employing tunnels and trenches for guerrilla-like warfare are Roman. After the uprising in Germania the insurgent tribes soon started to change defence from only local strongholds into utilising the advantage of wider terrain. Hidden trenches to assemble for surprise attacks were dug, connected via tunnels for secure fallback. In action often barriers were used to prevent the enemy from pursuing.