World War I
Trench warfare killed many soldiers. New weapons, such as machine guns, and long-range artillery had an increased rate of fire that cut down huge numbers of soldiers during mass charges, a tactic left over from older warfare.  The men on both sides took spades and dug holes because they did not want to be killed. The holes joined up into trenches until the lines of trenches went all the way from Switzerland to the North Sea. In front of the trenches was barbed wire to cut anyone who tried to climb over it and land mines to blow up anyone who tried to cross. Late in the war, poison gas also was an important weapon.