Static defense

Trench warfare is a type of land warfare using occupied fighting lines consisting largely of trenches, in which troops are significantly protected from the enemy's small arms fire and are substantially sheltered from artillery. The most famous use of trench warfare is the Western Front in World War I. It has become a byword for stalemate, attrition, sieges and futility in conflict.

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 1914–18, both sides constructed elaborate trench and dugout systems opposing each other along a front, protected from assault by barbed wire, mines, 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.

With the development of armoured warfare, emphasis on trench warfare has declined, but still occurs where battle-lines become static.

Field works are as old as armies. Roman legions, when in the presence of an enemy, entrenched camps nightly when on the move. In the early modern era they were used to block possible lines of advance. For example:

Nor were fortifications restricted to European powers. Elaborate trench and bunker systems were independently developed by the Maori, who successfully employed them as early as the 1840s to withstand British cannon, muskets, and an experimental poison-gas mortar, in the New Zealand Wars. British casualty rates of up to 45 percent, such as at the Battle of Ohaeawai in 1845, proved contemporary firepower was insufficient to dislodge defenders from a trench system.

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