Trench Warfare is a war tactic where opposing static defensive positions fire upon one another at range. Trench warfare was the prime tactic used on the western front during World War 1, where it produced a stalemate until the introduction of poison gas and tanks into the war, which forced trench lines to fall back or become relatively ineffective against armored foes. Trenches where often lined with machine guns, mines, and riflemen, and the ground between trenches provided artillery with a good vantage point for firing provided the enemy did not use smoke or the weather was permitting. The area between trenches is known as No-Man's Land. Today, trench warfare is obsolete against modern armies, but these defensive positions still provide great defense against soldiers that lack sufficient armor or air support.