The Gilder Lehrman Institute of American History Advanced Placement United States History Study Guide

Period 7: 1890-1945

World War I

War swept across Europe in the summer of 1914, igniting a global struggle that would eventually take nine million lives. World War I pitted the Allies (initially composed of Britain, France, Belgium, Serbia, and Russia, and eventually totaling eighteen nations including Japan, Italy, and the United States) against the Central Powers (Germany, Austria-Hungary, the Ottoman Empire, and Bulgaria). The assassination of the heir to the Austro-Hungarian throne in Sarajevo, Bosnia, set in motion a flurry of military mobilizations and failed diplomatic exchanges that led to Germany’s attack on Belgium and France in August 1914. In the early months of the war, Germany, France, and Britain dug defensive trenches, creating a complex system of earthworks along a western front that ran for 460 miles from the North Sea to Switzerland. Millions of soldiers would live and die in this trench deadlock over the next four years. Most Europeans rushed into battle without considering what a general war would mean. Americans, however, followed a completely different road to war, openly debating for two and a half years whether this was their war to fight. In 1914, President Woodrow Wilson declared that the United States would remain neutral. There were many first- and second-generation immigrants from both the Central Powers and the Allied nations in the United States, and they disagreed over which country had started the war and which country to support. Wanting both to stay out of the war and to prevent bitter divisions from ripping America apart, Wilson urged Americans to avoid “passionately taking sides” and to be “impartial in thought, as well as action.”[1]

Neutrality, however, turned out to be difficult to define and maintain. The dilemma was how to remain neutral without inflicting serious damage on the American economy. At first Wilson tried to limit the nation’s financial involvement in the war by banning private American bank loans to the belligerent nations. Secretary of State William Jennings Bryan believed the ban would bring the war to a speedy end by making it impossible for the combatant nations to buy what they needed to continue fighting. Wilson, however, lifted the ban in 1915. The Allies were running short of cash, and Wilson feared a widespread recession if those nations stopped buying American goods. By 1917 American banks were loaning Britain an average of $10 million a day to buy US goods. In the meantime, American trade with Germany dropped dramatically. Even if American manufacturers and banks had wanted to help Germany, trade became nearly impossible after the British navy blockaded Germany and cut the international cable between the United States and Germany. Germany retaliated with a new weapon, the U-boat or submarine, launching surprise attacks against merchant and military vessels to disrupt trade between Britain and the United States.

Unconditional submarine warfare soon created a diplomatic crisis in German–American relations. On May 7, 1915, a German U-boat sank the Lusitania, a British passenger ship sailing off the coast of Ireland; 123 Americans were among the victims. An outraged Wilson demanded that Germany pay reparations and accept the right of Americans to travel on any ship they wished. The Germans defended the sinking, pointing out that they had published notices in American newspapers warning passengers to stay off ships heading to the war zone. Germany also alleged that the Lusitania had been carrying munitions (a claim contested to this day). The sinking of the Lusitania was an ideological turning point for the United States, prompting Wilson to move away from his initial definition of neutrality being “impartial in thought, as well as action.” He now embraced neutrality as a concept that first and foremost gave neutral nations the indisputable right to trade and travel wherever they liked. Wilson’s insistence on protecting the rights of neutral nations put the United States on a collision course with Germany.

For the time being, Germany decided to honor Wilson’s demands. In August 1915 a German U-boat sank another British passenger ship, the Arabic, leaving two Americans dead. To placate Wilson, Germany issued the Arabic Pledge, which renounced surprise attacks on passenger ships. In the wake of another controversial torpedoing, Germany suspended unannounced attacks on merchant vessels with the Sussex Pledge in May 1916. By adhering to the pledges, Germany averted war with the United States in 1915 and 1916.

In January 1917, however, Germany decided to resume unconditional submarine warfare, fully aware that renewed surprise attacks on merchant and passenger ships would likely prompt the United States to declare war. The United States posed no immediate military threat to Germany, having made few substantial preparations for war. Germany reasoned that a massive U-boat campaign would prevent supplies from reaching Britain and France, forcing the Allies to sue for peace before the Americans could arrive in force overseas. German foreign minister Arthur Zimmermann hoped to further delay the arrival of American soldiers along the western front by stirring up trouble across the Atlantic. Attempting to benefit from recent tensions between the United States and Mexico, Zimmermann sent a telegram suggesting that Mexico start a border war with the United States if the United States and Germany went to war. In return, Zimmermann offered to help Mexico recover Texas, New Mexico, and Arizona (territory ceded in the nineteenth century). In one of the war’s greatest intelligence coups, British agents intercepted and deciphered the Zimmermann telegram. When the State Department released it to the press, many Americans viewed it as proof that Germany had hostile intentions against the United States. Further evidence of German aggression came in March when German U-boats sank three American merchant ships. Convinced that Germany threatened the nation’s territorial and economic security, and hopeful that by joining the Allied side the United States could play a leading role in shaping the peace, Wilson asked Congress for a declaration of war.

In his April 2, 1917, war address, Wilson cast the war’s purpose in broad, idealistic terms. America, he declared, had “no quarrel with the German people.” Instead, the United States was fighting against the “little groups of ambitious men” who used the German people as pawns to aggrandize their power. Wilson succinctly framed the war’s purpose in one phrase that has resonated in American foreign policy ever since: the world, he declared, “must be made safe for democracy.” The United States officially declared war against Germany on April 6, 1917. The nation did not declare war against Austria-Hungary until December 7, 1917, and was never at war with the Ottoman Empire or Bulgaria.

Wilson offered a more comprehensive description of the country’s war goals in his Fourteen Points speech to Congress on January 8, 1918. The Fourteen Points envisioned a world dominated by democracy, free trade, disarmament, and self-determination; sought to resolve territorial disputes in Europe; and proposed a league of nations to mediate international crises. Wilson explicitly linked the spread of democracy with the expansion of capitalism, a position that gained new urgency when the Communists prevailed in the 1917 Russian Revolution and began confiscating private property amid promises to redistribute wealth to peasants and workers. The United States and the new Soviet Union would continue to debate throughout the twentieth century whether spreading democracy meant increasing political rights and free trade or reallocating wealth.

The First World War was a total war, requiring the complete mobilization of American society. During the war, the federal government exercised unprecedented powers to centralize and coordinate the economy. The methods used to mobilize the manufacturing and agricultural sectors, select men for the military, regulate transportation, and distribute propaganda set precedents for how the federal government would respond to the crises of the Great Depression and World War II. The Committee on Public Information controlled the flow of information to shape public opinion about the war and disseminated patriotic posters, pamphlets, and films. The agency also recruited so-called Four-Minute Men (named for the time that it took to change reels for silent movies) to speak before audiences in movie halls, markets, fairs, and churches. The Food Administration organized a massive food conservation campaign around the slogan “food will win the war,” urging citizens to observe wheatless Mondays, meatless Tuesdays, and porkless Saturdays to save food for the troops. The War Industries Board ranked industries, so that those most critical to the war effort received raw materials ahead of nonessential businesses, while the Railroad Administration ran the nation’s railroads for the duration of the war. The National War Labor Board (made up of representatives from government, business, and labor) required industries that accepted government contracts to honor the eight-hour day and the forty-hour week, government-sponsored benefits that workers lost when the war ended. Wages increased slightly during the war, but the steel, copper, petroleum, and meatpacking industries all reaped tremendous profits by selling war-related goods to the government.

During the period of neutrality, Americans could freely voice their opposition to fighting against Germany. Once the nation was officially at war, however, the government curbed dissent. The 1917 Espionage Act made it a crime to obstruct military recruitment, to encourage mutiny, or to aid the enemy by spreading lies. The 1918 Sedition Act prohibited uttering, writing, or publishing “any abusive or disloyal language” concerning the flag, Constitution, government, or armed forces. Upholding the constitutionality of the Espionage Act in Schenck v. United States (1919), the Supreme Court agreed that Congress could curtail speech that created a “clear and present danger.” Writing for the majority, Justice Oliver Wendell Holmes Jr. concluded that “when the nation is at war many things that might be said in time of peace . . . will not be endured so long as men fight.”

World War I left several permanent marks on American society. The wartime emphasis on worker efficiency, conserving grain, and keeping alcohol away from soldiers in uniform hastened the adoption of the Eighteenth Amendment (1919) banning the sale, manufacture, and transportation of intoxicating liquors. A major demographic shift known as the Great Migration occurred when African Americans from the South moved north to take factory jobs, filling vacancies generated by booming wartime production, conscription, and the interrupted flow of immigrants from Europe. Women temporarily took on new roles in factories and offices as men left to serve in the wartime Army. Suffragists demanded that the nation thank these women for their wartime contributions by giving them the right to vote. The ratification of the Nineteenth Amendment in 1920 ended a decades-long campaign to secure voting rights for women.

Under the command of General John J. Pershing, the American Expeditionary Forces experienced both the horrors of trench warfare and the difficulties of conducting a war of movement during the sweeping attacks that slowly pushed the Germans back toward their own border in 1918. Key American engagements included battles at Cantigny, Belleau Wood, and Château-Thierry, which helped stop the German drive toward Paris in the spring of 1918. In the St. Mihiel and Meuse-Argonne offensives American soldiers took part in a multi-pronged Allied assault that ended when Germany requested an armistice. At 11:00 a.m. on November 11, 1918, men on both sides climbed out of the trenches to celebrate having survived the war. Overall, the Americans lost 53,400 troops on the battlefield and 63,100 to disease (the majority victims of the Spanish Influenza pandemic that killed over half a million Americans in 1918).

The Armistice ended active fighting in western Europe, but the Versailles Peace Treaty took months to negotiate. The final treaty required that Germany pay reparations and disarm. It also created a League of Nations. Wilson believed that this collective security organization would prevent another world war by giving member nations a place to mediate international disputes and coordinate joint-military actions to contain aggressor nations. Many Republicans, however, disagreed with the Democratic president’s rosy predictions of permanent peace. Opponents worried that by joining the League the United States would lose control of its own foreign policy. Membership might also invite international scrutiny of US armed interventions throughout Central America, where the United States was used to acting unilaterally. Isolationists and balance-of-power advocates joined forces to strenuously oppose joining the League, and their campaign gained momentum when a stroke (kept secret from the public) forced Wilson into seclusion for months. Wilson ultimately refused to compromise with his opponents, and the Senate rejected the treaty. Instead, the war officially ended for United States in October 1921 when the Senate ratified separate peace treaties with Germany, Austria, and Hungary. The United States never joined the League of Nations, but the Wilsonian goals of self-determination, free trade, disarmament, and spreading democracy continued to shape American foreign policy for decades to come.


[1] Woodrow Wilson, Message to Congress, 63rd Cong., 2d Sess., Senate Doc. No. 566 (Washington, 1914), 3–4.

Jennifer D. Keene, professor of history at Chapman University, is the author of The United States and the First World War (2000), Doughboys, the Great War and the Remaking of America (2001), and World War I (2006). She is currently working on a book detailing African American soldiers’ experience during the First World War and another on the significance of World War I for American society.


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