USCIS 128:101. Why did the United States enter World War I?

OpenAI. (2026). Why did the United States enter World War I?   [AI-generated infographic]. OpenAI.  Edited by Jennifer Gagliardi

World War I began in 1914, but the United States did not enter the war right away. At first, many Americans wanted the country to remain neutral and stay out of the fighting in Europe. President Woodrow Wilson also hoped the United States could avoid war.

The war was fought between two major groups. The Allied Powers included Great Britain, France, Italy, and Russia. The Central Powers included Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria.

One important reason the United States entered the war was because Germany attacked U.S. civilian and trade ships. Germany used submarines called U-boats to attack ships in the Atlantic Ocean. In 1915, a German submarine sank the British passenger ship RMS Lusitania. About 1,200 people died, including Americans. This shocked many people in the United States.

Another reason was that the United States wanted to support the Allied Powers. The United States traded heavily with Great Britain and France. Many Americans also felt cultural and political connections with these countries. As the war continued, many people believed an Allied victory was important for democracy and world stability.

The United States also opposed the actions of the Central Powers, especially Germany. Germany’s submarine attacks hurt international trade and threatened American lives and businesses.

In 1917, Americans became even more upset after learning about the Zimmermann Telegram. This was a secret message from Germany to Mexico. Germany promised to help Mexico recover land lost to the United States if Mexico joined the war against America. When the message became public, many Americans demanded stronger action.

Because of these events, President Wilson asked Congress to declare war on Germany in April 1917. He said the United States should help make the world “safe for democracy.”

After entering the war, American soldiers and supplies helped the Allied Powers. The fighting ended on November 11, 1918, known today as Veterans Day in the United States.

World War I was important because it changed the role of the United States in the world. After the war, the United States became more involved in international affairs and became a stronger world power.