trench warfare. Although trenches were used in ancient and medieval warfare, in the American Civil War, and in the Russo-Japanese War (1904–5), they did not become important until World War I. The introduction of rapid-firing small arms small arms, firearms designed primarily to be carried and fired by one person and, generally, held in the hands, as distinguished from heavy arms, or artillery .

Early Small Arms

The first small arms came into general use at the end of the 14th cent.
..... Click the link for more information. and artillery made the infantry charges of earlier wars virtually impossible, and the war became immobile, with the contenders digging thousands of miles of opposing trenches fronted by barbed wire. To break the stalemate various methods and new weapons were tried; tremendous artillery barrages sought to devastate the enemy and blow a gap in his trenches; trench mortars, hand grenades, poison gas, and tanks were used. It nevertheless remained a war of attrition, with artillery duels and infantry attacks behind creeping artillery barrages. The idea of an uninterrupted line defense held the imagination of the French and German general staffs between the two world wars, and they built lines of field fortifications known as the Maginot Line and the Siegfried Line. The advent of mechanized warfare mechanized warfare, employment of modern mobile attack and defense tactics that depend upon machines, more particularly upon vehicles powered by gasoline and diesel engines.
..... Click the link for more information. made it possible to circumvent such defenses, and World War II was a war of movement. However, in the last stages of the Korean war both sides established fortified positions across the Korean peninsula, and a stalemated situation similar to that of World War I came into play.

Bibliography

See L. Wolff, In Flanders Fields: the 1917 Campaign (1958).

trench warfare

Warfare in which the opposing sides attack, counterattack, and defend from sets of trenches dug into the ground. It was developed by Sébastien Le Prestre de Vauban in the 17th century for laying siege to fortresses. Its defensive use was first institutionalized as a tactic during the American Civil War. It reached its highest development in World War I. Little used in World War II, it reappeared in the Iran-Iraq War in the 1980s. A typical construction consisted of two to four parallel trenches, each dug in a zigzag, protected by sandbags, and floored with wooden planks. The parallel trenches were connected by a series of communication trenches dug roughly perpendicular to them. The first row was fronted by barbed wire and contained machine-gun emplacements; the rear trenches housed most of the troops. Increased use of tanks marked the end of trench warfare, since tanks were invulnerable to the machine-gun and rifle fire used by entrenched soldiers.