Trench Warfare Trench warfare was at the center of the fighting in World War I. Both sides constructed a network of trenches and dugout shelters, fortified by barbed wire, and fought from these trenches to wear the enemy down. In this photograph, members of the 369th Infantry, a segregated African American unit nicknamed the “Harlem Hellfighters,” occupy trenches to repel a German offensive into France in 1918. The Art Archive at Art Resource, NY