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The British cryptographic office known as “Room 40” decoded the Zimmermann Telegram and handed it over to the United States in late-February 1917. By March 1, its scandalous contents were splashed on the front pages of newspapers nationwide. Diplomatic relations between Germany and the United States had already been severed in early February, when Germany resumed unrestricted submarine warfare and began preying on U.S. vessels in the Atlantic. While many Americans remained committed to isolationism—President Woodrow Wilson had only just won reelection using the slogan, “He kept us out of war”—the Zimmerman cipher now served as fresh evidence of German aggression. Coupled with the submarine attacks, it finally turned the U.S. government in favor of entering the fray. On April 2, 1917, President Wilson abandoned his policy of neutrality and asked Congress to declare war against Germany and the Central Powers. The United States would cast its lot with the Allies four days later.