When war broke out in Europe, the United States immediately declared its neutrality. President Woodrow Wilson stated that America must be “impartial in thought as well as in action.”
For a century, the U.S. had stayed out of European affairs. Most Americans preferred to continue this policy. The country was growing into its potential, and had emerged as the world’s largest agricultural and industrial producer. It was in the midst of a shift from a rural to an urban society, which created both opportunities and challenges. Americans were focused on issues at home, rather than conflicts overseas.
On the other hand, most Americans had European roots. The majority leaned toward the Allies, thanks to a shared language and heritage with Britain and ties with France going back to the American Revolution. At the same time, a large population of German-Americans sympathized with their mother country, and many Irish-Americans held strong anti-British feelings.
Germany’s violation of Belgium’s neutrality further tilted U.S. public opinion toward the Allies. Allied propaganda exaggerated German brutality, but there was truth behind the claims -- German troops had burned down the medieval library at Louvain and had shot Belgian civilians and Allied sympathizers, including the British nurse Edith Cavell.
The war at sea also shaped U.S. opinion. Britain’s naval blockade was unpopular, as it prevented neutral nations from trading freely with both sides. At the same time, because of the blockade, the Allies were able to purchase far more U.S. goods and supplies than the Central Powers, often with loans from American financial institutions. This imbalance gave American businesses a vested interest in an Allied victory.
Also, although the British blockade was controversial, it was far less damaging than Germany’s policy of unrestricted submarine warfare. In early 1915, German U-boats began sinking all merchant ships going to or from Great Britain without warning. U.S. protests escalated until a German submarine sank the passenger liner Lusitania on May 7, killing 1,198 people, including 128 Americans. U.S. outrage exploded, and Germany halted unrestricted sinkings.
By this point, U.S. public opinion was firmly against Germany. A “preparedness” movement arose that argued the U.S. needed to build up its military in case it was pulled into the war. Preparedness was backed by many prominent Americans, including former president Theodore Roosevelt. It also gave rise to the Plattsburg Movement, a series of summer camps that taught attendees basic military skills.
However, there was still no widespread support for the war. In the end, preparedness advocates were able to achieve only a small increase in the U.S. Army and Navy. In November 1916, President Wilson’s peace position was validated as he won re-election with the slogan “He kept us out of war.” Yet less than four months later, he would ask the U.S. Congress for a declaration of war.