The battle that involved the use of trench warfare and became a hallmark of World War I is the Battle of the Somme, fought from July to November 1916. It was one of the largest battles on the Western Front, aimed at relieving pressure on French forces at Verdun and breaking through German lines. The battle is notorious for its horrific conditions and high casualty rates, with over one million soldiers wounded or killed. The use of trenches characterized the fighting, leading to a stalemate and illustrating the horrors of modern warfare. The Battle of the Somme ultimately became symbolic of the futility of trench warfare and the brutality of World War I.