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 ."

Airplanes aren't all there is to the new technology of war. Submarines launch torpedoes, and poison gas leaves soldiers blind and unable to breathe . Yet the killing machines are never enough. It is still men—huge armies of men—who are needed. Armies of men who dig themselves into trenches and kill men in other trenches. Both sides fight on, stuck in bloody mud, for four years. Eventually, nine million will die—more than all the people in New York City today . President Woodrow Wilson writes, "The world itself seems gone mad, and there is a sort of stern compulsion to keep sane amidst the general wreck and distemper."

The United States thinks the vast Atlantic can serve as a moat to keep it from Europe's troubles. But America is becoming a world power—and the world is shrinking. Woodrow Wilson hopes to be a peacemaker. But when German troops march into peaceful Belgium and when German submarines begin sinking ships—including passenger ships—Americans are horrified. In past wars there were rules of fair play. But the German U-boats give no warnings . Early in 1917, eight U.S. ships are sunk .

On the night of March 31, 1917, Woodrow Wilson gets out of bed and takes his portable typewriter to the south veranda of the White House. Mrs. Wilson brings him a bowl of milk and crackers from the kitchen. In the quiet of early morning, the president types out a message that is to become famous. He writes, "The present German submarine warfare against commerce is a warfare against mankind. It is a war against all nations. We are accepting the challenge. The world must be made safe for democracy." It is a presidential call for a declaration of war.

On April 2, Wilson speaks to Congress . He says, "It is a fearful thing to lead this great, peaceful people into war, into the most terrible and disastrous of all wars. But the right is more precious than peace, and we shall fight for things which we have always carried nearest our hearts—for democracy." Wilson gets the greatest ovation of his life. The congressmen cheer and cheer. The president goes back to his office. He looks at his aide. "Isn't it strange that men should cheer for war," he says. Then he puts his head on his desk and weeps .