United States Enters World War I Summary

  • Last updated on November 10, 2022

U.S. involvement transformed the Great War into a global conflict with worldwide ramifications.

Summary of Event

On April 2, 1917, Woodrow Wilson, president of the United States, stood before the combined members of the U.S. House of Representatives and Senate and asked for a declaration of war against Germany. “It is a fearful thing to lead this great peaceful people into war,” he concluded.“But the right is more precious than peace.” Four days later, on April 6, the United States was formally at war. World War I (1914-1918)[World War 01];U.S. involvement [kw]United States Enters World War I (Apr. 6, 1917) [kw]World War I, United States Enters (Apr. 6, 1917) [kw]War I, United States Enters World (Apr. 6, 1917) World War I (1914-1918)[World War 01];U.S. involvement [g]United States;Apr. 6, 1917: United States Enters World War I[04240] [c]Wars, uprisings, and civil unrest;Apr. 6, 1917: United States Enters World War I[04240] [c]World War I;Apr. 6, 1917: United States Enters World War I[04240] [c]Diplomacy and international relations;Apr. 6, 1917: United States Enters World War I[04240] Wilson, Woodrow [p]Wilson, Woodrow;World War I[World War 01] Bethmann Hollweg, Theobald von Gerard, James Watson Grey, Sir Edward Lansing, Robert Page, Walter Hines

The most enduring American propaganda image of World War I is James Montgomery Flagg’s “I Want You” Army recruiting poster with the compelling picture of Uncle Sam pointing his finger at prospective recruits.

(U.S. Army)

For two and a half years following the outbreak of the war in Europe in August, 1914, the United States had practiced a policy of neutrality. The U.S. government had lent money and supplies to the Entente Allies (Great Britain and France) but also had attempted to avoid antagonizing the Central Powers (Germany, Austria-Hungary, and the Ottoman Empire). Neutral U.S. ships carried arms and munitions to the Allies, and Germany, seeing its war effort threatened, attempted to restrict this trade by sinking U.S. ships, primarily through the use of submarine Submarines;World War I[World War 01] warfare. In 1914, 1915, and 1916, Germany announced increases in the kinds of neutral ships that would be subject to submarine attack, only to moderate its demands in the face of strong U.S. threats to break off diplomatic relations. During these years, Wilson made several sincere efforts to mediate the European dispute, but his attempts failed.

U.S. soldiers leave for France.


In early 1917, the German government determined to take a calculated risk. Effective February 1, Germany announced, a policy of unrestricted submarine warfare would begin, and any neutral ship, armed or not, that attempted to transport supplies to the British or French would be attacked. Two days later, Wilson’s administration broke off diplomatic relations with Germany. Addressing a joint session of Congress on February 3, the president explained that it was the only alternative “consistent with the dignity and honor of the U.S.” However, he stated, he was not heading toward war, which would come only if Germany indulged in overt acts against the United States.

These acts came in the form of an escalated German submarine campaign in which many U.S. and Allied vessels were sunk and massive numbers of lives were lost. Wilson’s response was to call for armed neutrality, but the subsequent interception by the British of an encoded message from German foreign secretary Alfred Zimmermann to Mexico’s German minister proposing an alliance should war break out (known as the Zimmermann note) raised the threat of Mexican involvement and brought the war closer to home. On April 2, 1917, Wilson made it clear before a joint session of Congress that armed neutrality was an insufficient response to German attacks, and on April 6, the United States formally declared war on Germany.


Why Wilson went on to ask for a declaration of war two months after breaking off diplomatic relations with Germany has been the subject of intense historical debate. Six major arguments have been advanced: (1) U.S. bankers and arms manufacturers forced Wilson to declare war because the Allies would not be able to repay their debts if they lost the war; (2) clever British propaganda tricked Americans into believing that moral wrong resided exclusively in Germany; (3) U.S. security would be endangered by a German victory, because Germany was bent on worldwide aggression; (4) public opinion in the United States demanded war; (5) German submarine warfare forced the United States into the war; and (6) by April, 1917, Wilson believed that peace without victory in Europe demanded that U.S. forces be sent overseas, so Wilson personally decided that a declaration of war was necessary.

The first four of these arguments have their enthusiastic proponents but lack persuasive evidence. By the end of the twentieth century, most historians tended to emphasize the final two arguments. German submarine policy determined the course of U.S. neutrality after 1914; Germany’s decision to begin unrestricted warfare in February, 1917, was a major reason for U.S. entrance into the war. Not to be discounted also was Wilson’s personal belief that he could bring about an idealistic peace in Europe only by helping the Allies defeat the Central Powers.

There can be no doubt of Wilson’s sincerity in believing that the United States must undertake a moral crusade by fighting a war “to end all wars.” In spite of his genuine unwillingness, Wilson opted for war largely through calculations of cost and benefit. His policy of armed neutrality had turned out to be a failure in terms of the loss of lives and property it had entailed and the enemies it had created at home. In addition, it had not been able to release the tensions of war, let alone create the ground for an ideal peace settlement. For Wilson, the raging war was inglorious, a macabre slaughter of millions of innocent people, a disaster, and a sheer horror. The world needed a new order such as he had outlined in his “peace without victory” address. In the end, the president was left with no choice but to seek that order by entering the war. U.S. intervention would crush the might of Germany and bring Allied victory surely and swiftly. However, when the aftermath saw no restoration of international order, critics blamed Wilson’s idealism for subsequent problems. World War I (1914-1918)[World War 01];U.S. involvement

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Buehrig, Edward H. Woodrow Wilson and the Balance of Power. Bloomington: Indiana University Press, 1955. Pointed analysis of close Anglo-American political, economic, military, and cultural relations and the corresponding decline in relations with Germany. Explains U.S. entry into the war as shaped by German aggression at sea and the urge to protect British naval superiority.
  • citation-type="booksimple"

    xlink:type="simple">Esposito, David M. The Legacy of Woodrow Wilson: American War Aims in World War I. Westport, Conn.: Praeger, 1996. Argues that Wilson was motivated by his belief that Germany was a threat to U.S. national security and that, forced into the war, he wanted U.S. intervention to be decisive so that the United States would hold a dominant position in a postwar peace conference.
  • citation-type="booksimple"

    xlink:type="simple">Ferrell, Robert H. Woodrow Wilson and World War I, 1917-1921. New York: Harper & Row, 1985. Superb study covers both domestic and foreign developments. Focuses on Wilson as a reluctant and tragic figure amid a national crisis.
  • citation-type="booksimple"

    xlink:type="simple">Gregory, Ross. The Origins of American Intervention in the First World War. New York: W. W. Norton, 1971. Describes the background to U.S. entry into the war, with focus on Wilson’s administration and the domestic forces that shaped its decisions. Examines the outside forces in London, Berlin, and Paris that influenced the course of U.S. policy.
  • citation-type="booksimple"

    xlink:type="simple">Kennedy, David M. Over Here: The First World War and American Society. 25th anniversary ed. New York: Oxford University Press, 2004. Study of the impact of World War I on U.S. society and culture explores topics of race, gender, and radicalism.
  • citation-type="booksimple"

    xlink:type="simple">Link, Arthur S. Woodrow Wilson: Revolution, War, and Peace. Arlington Heights, Ill.: Harlan Davidson, 1979. Wilson’s chief biographer and editor of his papers argues that Wilson, imbued with only the highest motives, was influenced by both moral and practical factors. Provides extensive description of events in belligerent nations and their impact on the United States.
  • citation-type="booksimple"

    xlink:type="simple">May, Ernest R. The World War and American Isolation, 1914-1917. Cambridge, Mass.: Harvard University Press, 1959. Based on multiple archival sources, posits that Wilson, after much soul-searching, could not stay out of war because of U.S. interests and European pressures. Asserts that Wilson’s policy was more correct than incorrect.

Outbreak of World War I

World War I

Germany Begins Extensive Submarine Warfare

Spain Declares Neutrality in World War I

International Congress of Women

U.S. Curtails Civil Liberties During World War I

Espionage and Sedition Acts

United States Establishes the War Industries Board

Meuse-Argonne Offensive

Treaty of Versailles

Categories: History