A Fully Mechanized War

The military technology of World War I resulted in vast casualties and destruction. Unfortunately, these weapons were improved upon, creating even greater wreckage in World War II:

Atomic Bomb:

                       The atomic bomb was by far the deadliest weapon created in the World War I/World War II time period. It was used only twice, and has
   never been used in wartime again. This weapon of mass destruction was the product of the Manhattan Project, a top-secret research
                       project. Two bombs, Little Boy and Fat Man, were dropped on Hiroshima and Nagasaki, respectively.

Fighter Planes:

                       In World War I planes were used mainly for reconnaissance. Pilots would occasionally engage in dogfights, but these skirmishes had
                       little effect on the war. There were many defects with the planes, and pilots would often destroy their own propellers with their guns.
                       In World War II however, the planes were improved upon and were used for countless bombing missions, including the German blitzkrieg
                       of London and the Japanese attack on Pearl Harbor. The fighter planes also fired upon troops during battles, terrifying soldiers.

Tanks:

                      Tanks were also upgraded, inflicting much more damage in World War II than they did in World War I. British tanks were not nearly as
                      powerful as German ones, however. German tanks played a major role in the German Campaign in Northern Africa. This operation was
                      led by Erwin Rommel, or the Desert Fox. Rommel maneuvered the Germans quick moving tanks around Allied forces, winning several
                      victories.

Many other extremely deadly weapons were used on both sides of the war. The World Wars were the largest conflicts in history, with mass casualties for the Allies and Axis alike.