Trench warfare. 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.