Mass-production in the late 19th century revolutionized how wars were fought. Rifles and machine guns became commonplace weapons on battlefields. New guns had the capability of attacking an opponent from longer ranges, making it easier for troops to attack from concealed areas. Frontal assaults became disastrous, and horse-mounted cavalry units became obsolete, ushering in the age of mechanized warfare.
In attempts to break the stalemate presented by trench warfare, the Germans utilized their well-established chemical industry to produce both chlorine and mustard gases. Although poison gas had been banned, both sides resorted to it as the war dragged. Advancements in long-range artillery technology meant that soldiers hidden within trenches could be hit from above by explosives and gas. The airplane also made its military debut during World War I, adding the threats of aerial bombing, strafing (fly-by gunfire), and access to detailed observations of troop movements to the long list of a soldier’s worries. Flying above the fray, airplanes observed enemy lines, providing crucial tactical information. Although some fighter planes were used, they were not as fierce or as powerful as their contemporary counterparts. Instead, planes were fraught with mechanical problems making them extremely dangerous.
While the airplane was still in its infancy, tanks were well received by all armies. Although soldiers seldom dared expose themselves from a trench, the protection of an armored tank allowed tankers to wreak havoc on enemy positions from relative safety.
As planes and tanks were developed in response to trench warfare, submarines became critical to maintain control over the shipping routes that supplied the trenches. Submarine warfare also played a major role in global politics. Germany’s policy of unrestricted submarine warfare, which led to the sinking of the Lusitania, was one of the reasons the U.S. entered the war.