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
Methods to defeat it are rudimentary. Prolonged artillery bombardment could damage them, but not reliably. The first soldier meeting the wire could jump onto the top of it, hopefully depressing it enough for those that followed to get over him; this still took at least one soldier out of action for each line of wire. In World War I, British and Commonwealth forces relied on wire cutters, which proved unable to cope with the heavier gauge German wire. The Bangalore torpedo was adopted by many armies, and continued in use past the end of World War II.