<Ul> <Li> </Li> <Li> </Li> <Li> </Li> </Ul> <P> Trench warfare is a type of land warfare using occupied fighting lines consisting largely of military trenches, in which troops are well - 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 . </P> <P> 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 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 . </P> <P> With the development of armoured warfare, emphasis on trench warfare has declined, but still occurs wherever battle - lines become static . </P>

What caused trench warfare in world war 1