What caused the United States to enter World War I?

The United States entered World War I for several reasons:

1. Unrestricted Submarine Warfare: Germany had declared unrestricted submarine warfare in the Atlantic, which meant they would sink any ship without warning. This included American ships carrying goods to Britain. The sinking of the Lusitania, a British passenger ship, by a German submarine in 1915, which resulted in the deaths of 1,198 people, including 128 Americans, outraged the American public.

2. Zimmerman Telegram: In 1917, British intelligence intercepted a secret telegram sent by German Foreign Secretary Arthur Zimmerman to Mexico. The telegram proposed a military alliance between Germany and Mexico if the United States entered the war. In return, Germany would help Mexico recover the territories it had lost to the United States in the Mexican-American War. This telegram was made public and further pushed the United States towards war.

3. Economic Interests: The United States had strong economic ties with the Allies, particularly Britain and France. American banks had lent large sums of money to these countries, and American businesses were supplying them with war materials. If the Allies were to lose the war, it would have a significant impact on the American economy.

4. Ideological Reasons: President Woodrow Wilson and many Americans believed in the idea of making the world "safe for democracy." They saw the Central Powers, particularly the autocratic regimes of Germany and Austria-Hungary, as a threat to democracies worldwide.

These factors combined led to the United States Congress declaring war on Germany on April 6, 1917, thus entering World War I.