- German U-boat Attacks on American Ships: The unrestricted German submarine warfare against Allied shipping, which resulted in the sinking of several American merchant ships and the loss of American lives, was a significant factor in pushing the United States towards war. The most notable incident was the sinking of the British passenger liner RMS Lusitania in 1915, which resulted in the death of over 100 American civilians.
- Zimmermann Telegram: The interception and leaking of the Zimmermann Telegram, a secret diplomatic message from Germany to Mexico proposing an alliance against the United States, added further fuel to the growing anti-German sentiment in America.
- Moral Indignation: Many Americans were moved by the stories of atrocities committed by German forces in Belgium and France during the early stages of the war, creating a sense of moral obligation to intervene and stop the perceived aggression.
- Economic Ties and Loans: The United States had significant economic ties with the Allied powers, particularly Great Britain and France, and had lent them large sums of money during the conflict. The prospect of an Allied defeat and the subsequent loss of these loans and investments played a role in the decision to enter the war.
Differences from Other Countries' Reasoning
- American Neutrality: The United States had initially maintained a policy of neutrality in the early years of the war, despite growing pressure from both the Allies and the Central Powers. American reasoning for entering the war was not driven by territorial ambitions or geopolitical interests, unlike other European powers directly involved in the conflict.
- Moral Imperative: The American emphasis on moral indignation as a reason for entering the war distinguished its motivations from those of other nations, whose decisions were largely rooted in strategic and political considerations.
- Ideals and the Peace Settlement: President Woodrow Wilson's Fourteen Points, a set of principles aimed at achieving a just peace and establishing a new international order, further shaped American reasoning for entering the war and reflected the nation's idealism.