When World War I began, the United States adopted a policy of neutrality. The majority of Americans favored staying out of foreign wars, which is what they considered World War I to be. However, Germany itself provoked the United States with its policy of unrestricted attacks on ships in the North Atlantic.
In 1915 a German cruiser sunk a private American vessel. The Germans apologized, calling it a mistake, and the U.S. was mollified for a time. Later in 1915 a German U-boat sank a British passenger ship, the Lusitania, off the Irish coast. Of 1,959 passengers, 1,198 were killed, including 128 Americans. The attitudes of Americans began to turn against Germany, especially since Great Britain was one of the United States’s biggest trade partners.
Still, Woodrow Wilson, Congress and most of American sentiment was against entering this war that really didn’t threaten citizens in the United States. But, in 1917, Germany became desperate to break the stalemate of the Western Front and announced that it was resuming unrestricted warfare in what it termed “war zone waters,” meaning the North Atlantic. Three days later the United States broke diplomatic relations with Germany. In late March 1917 Germany sank four U.S. merchant ships. On April 2, 1917, President Wilson asked for a declaration of war from Congress. Four days later that request was granted.
In June 1917 some 14,000 American troops arrived in France, led by General John Pershing. Pershing made a visit to a site sacred to the French, the tomb of the Marquis de Lafayette, who had come to the aid of the new American republic during the Revolutionary War. Pershing is reported to have said, “Lafayette, nous voila!” (“Lafayette we are here!”). By this gesture, America said it was joining the war for the same reason Lafayette had come to the aid of the Americans: a hatred of autocracy and a desire to make the world a better, safer place.
The entrance of the United States proved to be a turning point in World War I. With fresh troops and the wealth of materiel available from the United States, the tide shifted in the Allies’ favor, leading to the end a year and five months later. It also marked a fundamental shift in America’s role on the world stage. By raising the American flag over French soil, the United States signaled it would bring its standard to the defense of liberty wherever necessary, and all but guaranteed its participation in World War II, still over 20 years in the future at that time.
This entry into World War I also positioned the United States as a world player who would ultimately engage in a long ideological battle with another country that was transformed by World War I: Russia, in its incarnation as the Soviet Union.