As a historian with a focus on the 20th century, I can provide a comprehensive analysis of why the United States decided to enter World War 1. The decision was not made lightly and was influenced by a variety of factors, including economic interests, political considerations, and the evolving nature of the conflict itself.

Economic Interests
The United States had become a significant economic power by the early 20th century, with a growing stake in international trade. The war in Europe disrupted international commerce, affecting American businesses and the economy. The U.S. was supplying the Allies with war materials and food, becoming increasingly entangled in the conflict's economic web. The British naval blockade of Germany hindered German trade, while the U.S. maintained a policy of neutrality. However, the U.S. was effectively favoring the Allies by trading with them, which led to a significant economic relationship that would be jeopardized if the Allies were to lose the war.

Political Considerations
President Woodrow Wilson was re-elected in 1916 with the slogan "He kept us out of war," reflecting the strong anti-war sentiment among the American public. However, as the war continued, the political landscape in the U.S. began to shift. The sinking of the Lusitania in 1915, although not the immediate cause for U.S. entry, was a significant event that galvanized public opinion against Germany. The Zimmermann Telegram, intercepted in 1917, revealed a German plan to incite Mexico to attack the United States, which further eroded public trust in Germany and increased the perception of a direct threat to U.S. national security.

**The Resumption of Unrestricted Submarine Warfare**
In 1917, Germany, determined to win its war of attrition against the Allies, announced the resumption of unrestricted submarine warfare in war-zone waters. This decision was a direct challenge to the United States, as it threatened American lives and the country's economic interests. The sinking of the American liner Housatonic by a German U-boat shortly after the announcement was a clear act of aggression that could not be ignored by the U.S. government.

Public Opinion and Propaganda
Public opinion in the U.S. was heavily influenced by propaganda from both sides of the conflict. However, as the war progressed and the nature of the conflict became more brutal, the American public began to see the war as a fight for democracy and freedom against autocracy and militarism. This narrative, coupled with the direct threats to American lives and interests, made it increasingly difficult for the U.S. to maintain neutrality.

The Final Decision
The culmination of these factors led to the U.S. declaration of war against Germany on April 6, 1917. The decision was not made in haste; it was the result of a complex interplay of economic, political, and strategic considerations. The U.S. entry into the war marked a significant turning point, providing the Allies with a much-needed influx of manpower, resources, and moral support.

In summary, the United States entered World War 1 due to a combination of economic interests, political pressures, direct threats to American lives and interests, and a shift in public opinion that framed the war as a moral and ideological struggle.

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In 1917, Germany, determined to win its war of attrition against the Allies, announced the resumption of unrestricted warfare in war-zone waters. Three days later, the United States broke diplomatic relations with Germany, and just hours after that the American liner Housatonic was sunk by a German U-boat.read more >>