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 warfare
At 3.10 on June 7, 1917, a series of mines was detonated by the British to launch the Battle of Messines. The average mine contained 21 tons of explosive and the largest, 125 feet beneath Saint-Eloi, was twice the average at 42 tons. As remarked by General Plumer to his staff the evening before the attack: