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America Enters the WarThe U.S. Entry into the War (Jan-Apr 1917)

Although most of the American public was sympathetic to the Allies, the United States stayed neutral for nearly three years. However, in early 1917, a series of events finally drew America into the war.

On February 1, Germany resumed unrestricted sub- marine warfare. Britain’s naval blockade was causing severe shortages for Germany’s military and its civilian economy. Germany saw no reason to continue holding back its most effective naval weapon, especially considering how unprepared the U.S. was for war. German U-boats once again began sinking all ships travelling to or from Allied ports. In response, the United States broke off diplomatic relations with Germany.

Then, in mid-February, the British presented the American government with a telegram they had inter- cepted from Germany’s Foreign Minister Arthur Zim- merman to its Ambassador to Mexico. The message promised to help Mexico recapture territory it had lost to the United States in the Mexican-American War (1846-48) if Mexico joined Germany as an ally.  The Zimmermann Telegram (as it came to be called) was published in U.S. newspapers on March 1, further feeding U.S. outrage.

In March, the Germans sank five U.S. merchant ships, with the loss of dozens of American lives. In addition, the fall of the Tsar’s regime in Russia simplified the moral argument for the Allied cause: the war was now between democratic nations and autocratic empires.

On April 2, President Wilson went to the U.S. Congress to formally ask it to declare war on Germany. The Senate granted Wilson’s request two days later, followed by the House of Representatives on April 6. The United States had joined the war.

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Lessons/resources

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More resources/lessons

» Chronicling America: Uncovering a World at War

Students analyze newspaper articles to understand and discuss the diversity of public opinion regarding the U.S. entry into World War I.  |  National Endowment for the Humanities

» United States Entry into World War I: A Documentary Chronology (3 Lessons)

Three lessons: (1) Two Diametrically Opposed Views; (2) Some Hypotheses About U.S. Entry; (3) A Documentary Chronology.  Can be used individually or as an integrated unit.  |  National Endowment for the Humanities

» U.S. Entry into WWI

Explores U.S. decision to go to war through the lens of President Wilson's speech and Howard Zinn's A People's History of the United States.  |  Stanford History Education Group

» World War I: What Are We Fighting For Over There?

Students will use historical primary sources to explore different perspectives on American involvement in the First World War.

» Zimmermannland

Students will analyze the context of the telegram from the perspectives of the U.S., Mexico, and Germany; examine the reaction in the Southwestern U.S. states that Germany promised to return to Mexico  |  The National World War I Museum & Memorial

» The Zimmermann Telegram

Online lesson involving analysis of the coded message and discussion on its impact.  |  National Archives

» Topics in Chronicling America - The Zimmerman Telegram

Links to newspaper coverage of Zimmermann Telegram episode. (NOTE: Summary of events mistakenly states Wilson was aware of telegram when U.S. broke off relations with Germany)  |  Library of Congress

» Unrestricted U-Boat Warfare: The German naval tactic of WWI

Article and video clip on the German tactic most responsible for America's entry into the War.  |  The National World War I Museum & Memorial

» Zimmermann Telegram: Germany's secret proposal to Mexico, discovered

Summary, images, and interactive timeline.  |  The National World War I Museum & Memorial

» Library of Congress: World War I

Homepage for the Library of Congress' extensive WWI collections and resources.  |  Library of Congress