AT THE BEGINNING of the twentieth century, countries in Europe competed to see which would be the most powerful. As their armies and navies grew, some countries feared attack and made alliances, promising to defend each other in the event of war. These alliances were tested in 1914 by the assassination of the heir to the Austro-Hungarian Empire. One nation after another declared war, and Europe was split in two: the Allied Powers—including Great Britain, France, and Russia—against the Central Powers—Germany, Austria-Hungary, Bulgaria, and the Ottoman Empire. It was called the Great War by Americans, and before it ended in 1918, countries all over the world were drawn into the battle.
Technology had made it possible to fight war in new ways. Battles were carried out using airplanes, submarines, and tanks. Soldiers attacked with long-range artillery, machine guns, flamethrowers, and poison gas. Troops communicated by means of field telephones, laying wire as they moved. Some hoped these scientific advances would ensure a short war. Instead, though millions died, the war dragged on for over four years.
The United States entered the Great War on April 6, 1917, to support the Allied Powers. Along with modern equipment, American soldiers on the front lines used pigeons to stay in
