The war began in Europe. At first, the Central Powers—Germany, Austria, and Turkey—fought the Allies—England, France and Russia. Before it finished, many other nations were involved. Like most wars, it was not inevitable; it came about because of national pride, the struggles of empires for territory and profit, and human error and bad judgment. It left open wounds that refused to heal. It changed the fate of the world, but no one knew that when it started.

In England, young men hurry to enlist—it seems noble and heroic to do so. Besides, they are afraid the war will be over before they get a chance to fight. No one believes it will last long. The president of the United States, Woodrow Wilson , calls the war "a distant event." He says, "The United States must be neutral, in fact as well as in name. There is such a thing as a man being too proud to fight." Wilson has ideas on foreign affairs that are different from those of most world leaders. He is part of a progressive movement within the Democratic Party. He is not an imperialist, and he makes it clear he wants to stay out of the war. But World War I is worse than anyone could have imagined. What had seemed just a quarrel turns to horrible, endless slaughter. And new inventions—like the Wright brothers' airplanes—which were intended to do good—become instruments of death.

At first airplanes are used to scout enemy territory. Fliers lean out of cockpits and shoot enemy pilots with pistols. Then a new invention allows pilots to synchronize machine guns with propeller blades. And then bombs are brought aboard and dropped by hand over the plane's side. Technology changes seem to come overnight. T. G. Sopwith, who built fighter planes for Great Britain, said, "We literally thought of, designed, and flew the airplane in a space of about six or eight weeks ."