APUSH Unit 7 Notes: The Great War’s Aftermath and the Transforming 1920s

World War I: Military and Diplomatic

Why World War I pulled the United States into global power politics

At the start of World War I in 1914, the United States tried to follow a tradition many Americans thought was both morally right and strategically smart: stay out of European wars. Neutrality meant the U.S. government did not formally take sides militarily, and Americans could imagine themselves as peacemakers rather than participants. But neutrality was hard to maintain in a modern, interconnected economy. The U.S. traded heavily with the Allied Powers (especially Britain and France), American banks made large loans to the Allies, and news coverage often portrayed Germany negatively—especially after German submarine attacks.

What matters for APUSH is not just that the U.S. entered the war in 1917, but why that decision made sense to many Americans at the time and how it changed the role of the federal government, civil liberties, and America’s place in the world. World War I accelerated a shift: the U.S. was no longer a nation that could comfortably ignore European affairs.

A common misconception is that a single event “caused” U.S. entry. In reality, several pressures built over time—economic ties to the Allies, German unrestricted submarine warfare, and the Zimmermann Telegram—until neutrality became politically unsustainable.

The road to war: neutrality, trade, and submarine warfare

Even while neutral, the U.S. economy became linked to an Allied victory. Britain’s powerful navy restricted trade with Germany, while Germany tried to counter Britain through submarine warfare. German U-boats targeted shipping headed for Allied ports, sometimes sinking neutral ships.

Two key flashpoints:

• Lusitania (1915): A German submarine sank the British passenger liner, killing over a hundred Americans. This did not immediately bring the U.S. into the war, but it shifted public opinion and pressured President Woodrow Wilson to respond.
• Sussex Pledge (1916): After another submarine incident, Germany promised to limit attacks on passenger ships. The pledge showed Germany understood the U.S. could become an enemy—but it was temporary.

In early 1917, Germany resumed unrestricted submarine warfare, calculating it could starve Britain into surrender before American troops could arrive in decisive numbers.

Then came the Zimmermann Telegram (1917)—a secret German message proposing an alliance with Mexico if the U.S. entered the war, hinting Mexico might regain territory lost to the U.S. This inflamed American opinion and made the conflict feel more directly threatening.

Wilson asked Congress for a declaration of war in April 1917, framing it as a defense of American rights and a fight to make the world “safe for democracy.”

Mobilizing to fight: how the U.S. built a war effort

When the U.S. entered the war, it had to convert rapidly from peace to wartime. This required mass mobilization—raising an army, producing weapons, transporting troops, and maintaining civilian support.

Building the military

The U.S. relied heavily on the Selective Service Act (1917) to draft soldiers. Rather than depending on volunteers alone, the federal government used conscription to create a force large enough for modern industrial war.

American troops—the American Expeditionary Forces (AEF) under General John J. Pershing—arrived in Europe in significant numbers in 1918. Pershing insisted that American units fight as a distinct force rather than being fully absorbed into British and French units, which mattered for U.S. national pride and postwar influence.

Fighting the war (military realities)

World War I was shaped by industrial technology. Trench warfare and machine guns made frontal assaults extremely deadly; artillery and poison gas added to the devastation. In response to U-boats, the Allies used the convoy system, grouping merchant ships with naval escorts to reduce losses.

By 1918, fresh American troops helped the Allies sustain offensives such as the Meuse-Argonne Offensive (one of the major U.S. military operations). Germany, facing military exhaustion and domestic unrest, agreed to an armistice on November 11, 1918.

It’s easy to overstate America’s battlefield role compared with years of fighting by European armies. A more accurate way to think about it is: the U.S. provided a crucial surge of manpower and resources at a moment when the Allies were strained and Germany was gambling on time.

The home front: federal power, propaganda, and civil liberties

War required not only soldiers but also national coordination. The federal government expanded its role dramatically.

• The War Industries Board coordinated industrial production and encouraged standardization.
• The Food Administration (associated with Herbert Hoover) promoted conservation rather than strict rationing.
• The government financed the war through taxes and Liberty Bonds, encouraging ordinary Americans to “buy in” financially.

To shape public opinion, the government used the Committee on Public Information (CPI) led by George Creel. The CPI used posters, films, speeches, and “Four Minute Men” to rally support. This matters because it shows how modern war involves information management, not just weapons.

Civil liberties during wartime

Wartime fear often leads governments to limit dissent. The U.S. passed:

• Espionage Act (1917): targeted interference with the war effort and draft.
• Sedition Act (1918): extended penalties to “disloyal” or critical speech about the government and war.

In Schenck v. United States (1919), the Supreme Court upheld restrictions on anti-draft speech, reasoning that speech posing a “clear and present danger” could be limited in wartime.

A common student mistake is to treat these laws as purely about “national security.” On APUSH, you should be able to argue both sides: supporters saw them as necessary for winning; critics saw them as violations of First Amendment principles and tools to suppress political radicals.

Social change during and after the war

World War I intensified long-term trends and created new tensions:

• Great Migration: Many African Americans moved from the rural South to northern cities, seeking industrial jobs and escaping Jim Crow violence. This reshaped urban politics and culture but also contributed to racial conflict and competition for jobs and housing.
• Women’s work expanded in some industries and volunteer roles. The war strengthened arguments for women’s citizenship and political participation, contributing to the momentum behind the Nineteenth Amendment (1920), which granted women the right to vote.

The peace settlement: Wilsonian idealism vs. political reality

After the armistice, Wilson tried to shape the postwar world. His Fourteen Points promoted ideas like freer trade, open diplomacy, and national self-determination (though applying that ideal consistently was difficult in multiethnic empires).

The centerpiece was the League of Nations, intended as an international organization that could deter aggression through collective security.

But the Treaty of Versailles (1919) did not simply implement Wilson’s vision. European Allies, especially France, wanted harsh terms for Germany. The treaty included territorial changes and imposed blame and heavy burdens on Germany.

Why the U.S. rejected the Treaty of Versailles

The U.S. Senate must ratify treaties by a two-thirds vote. Opposition formed around Article X of the League covenant (often associated with collective security obligations). Critics feared the League could pull the U.S. into future wars without Congress declaring war.

Key factions:

• Irreconcilables: opposed the treaty and League under any conditions.
• Reservationists (including Senator Henry Cabot Lodge): wanted amendments or reservations limiting U.S. obligations.

Wilson refused to compromise effectively, and the Senate rejected ratification. The U.S. never joined the League of Nations.

This is a major turning point: it highlights the tension between internationalism and isolationism and shows how domestic politics can shape foreign policy.

Exam Focus

• Typical question patterns:
  • Compare motivations for U.S. entry into WWI with earlier foreign policy traditions (neutrality, Monroe Doctrine, etc.).
  • Evaluate how WWI expanded federal power and affected civil liberties.
  • Analyze why Wilson failed to secure Senate ratification of the Treaty of Versailles.
• Common mistakes:
  • Treating “Lusitania” as the sole cause of entering the war—explain the sequence (submarine warfare + Zimmermann + economic ties).
  • Describing the League debate as purely partisan—include constitutional concerns and factions (irreconcilables vs. reservationists).
  • Ignoring the home front—many AP questions focus on propaganda, labor, migration, and civil liberties.

The 1920s: Innovation, Culture, and Tension

What made the 1920s feel “modern”

The 1920s are often remembered for prosperity, jazz, and consumer goods. What made the decade historically important is that it accelerated changes in how Americans lived: work shifted toward mass production, leisure became commercialized, cities grew in cultural influence, and new technologies reshaped daily routines.

At the same time, the decade exposed deep tensions about what America should be. A useful way to understand the period is as a clash between:

• Modernism: embracing science, consumer culture, and changing social norms.
• Traditionalism: defending religious authority, older moral codes, and established social hierarchies.

These tensions didn’t stay “cultural.” They influenced politics, law, immigration policy, and race relations.

Economic innovation: mass production and consumer culture

A key economic shift was the growth of mass production, especially associated with automobiles and consumer appliances. Henry Ford popularized the moving assembly line, which increased productivity and helped lower the cost of cars like the Model T. The deeper point isn’t just “cars existed,” but that mass production changed labor (more repetitive tasks), business organization, and consumer expectations (goods should be affordable and widely available).

Electricity spread more widely, powering household appliances and changing how long people could work and socialize. The radio created a shared national culture—Americans in different regions could listen to the same music, news, and advertising.

Advertising and buying on credit

The 1920s saw a stronger national advertising industry. Companies didn’t just sell products; they sold lifestyles and identities. Installment buying (buying on credit over time) let middle-class consumers purchase expensive goods immediately.

A common misconception is that the 1920s prosperity reached everyone equally. Many industrial workers benefited, but farmers faced serious economic hardship as agricultural prices fell after wartime demand ended. That rural economic stress contributed to political resentment and made “culture wars” sharper.

Politics of the decade: pro-business government and scandal

Presidents Warren G. Harding, Calvin Coolidge, and Herbert Hoover generally favored a pro-business environment and limited regulation (though “laissez-faire” should not be treated as absolute—government still shaped markets through tariffs and other policies).

Harding’s administration became associated with scandal, most famously the Teapot Dome scandal, involving bribery related to oil reserves. The significance is not just corruption; it fed cynicism about government and reinforced arguments that politics served powerful interests.

Cultural change: Harlem Renaissance, mass media, and new social norms

Harlem Renaissance

The Harlem Renaissance was a flourishing of African American art, literature, and music centered in Harlem, New York, influenced by the Great Migration and urban community-building. Writers and artists explored themes of racial pride, struggle, and modern identity. The movement matters because it shows African Americans shaping national culture while still facing segregation and racism.

Jazz and popular culture

Jazz became a symbol of modern life—improvisational, urban, and associated with nightlife. Films (including silent movies) and celebrity culture helped create national trends.

Women and changing norms

The decade is associated with the “flapper” image—young women challenging older expectations in dress and behavior. It’s important not to reduce women’s history to a stereotype. Women’s lives varied by region, class, and race. Still, the decade did reflect changing public conversations about gender roles, leisure, and autonomy.

Prohibition: moral reform and unintended consequences

Prohibition refers to the national ban on the manufacture, sale, and transport of alcoholic beverages, established by the Eighteenth Amendment (1919) and enforced through the Volstead Act.

To understand Prohibition, think about cause and mechanism:

• Why it happened: long-term temperance activism, Progressive Era faith in using government to improve society, and wartime anti-German sentiment (since some breweries were linked in the public mind with German Americans).
• How it worked: a constitutional amendment required federal and local enforcement.
• What went wrong: enforcement was uneven; illegal markets expanded; bootlegging and speakeasies became common; organized crime profited.

Prohibition is a strong example of how a policy can reflect cultural values but produce unintended outcomes when large portions of the public resist compliance.

Modernism vs. fundamentalism: the Scopes Trial

The 1920s saw a clash over religion and science, especially around teaching evolution. The Scopes Trial (1925) in Tennessee—about whether a teacher could teach evolution in violation of state law—became a media spectacle. Although the immediate legal outcome was limited, the trial symbolized a broader conflict: who should define truth and morality in public life—traditional religious authority or modern scientific ideas?

A frequent student error is to treat this as purely “North vs. South.” The conflict was national, though it often appeared most visibly in rural vs. urban contexts.

Racial and ideological tensions: Red Scare, labor conflict, and the KKK

The early postwar years included the First Red Scare (1919–1920), driven by fear of communism and anarchism after the Russian Revolution and a wave of strikes in the U.S. The government conducted the Palmer Raids, targeting suspected radicals and immigrants. Some threats were real, but the raids also violated civil liberties and encouraged guilt-by-association.

The 1920s also saw the resurgence of the Ku Klux Klan (KKK)—not just in the South, but nationally. The Klan promoted white Protestant supremacy and targeted not only African Americans but also Catholics, Jews, and immigrants. This shows how racial and religious intolerance could grow alongside “modern” consumer culture.

Example: turning cultural tension into an argument (LEQ-style)

If you were asked to evaluate the extent to which the 1920s were a period of cultural conflict, a strong thesis would connect multiple arenas:

• Modernism: radio, movies, consumerism, Harlem Renaissance.
• Traditionalism: Prohibition, fundamentalism, nativism.
• Conflict point: Scopes Trial and KKK illustrate backlash; immigration restriction laws show political consequences.

The key is to show that the decade wasn’t simply “roaring prosperity,” but a push-and-pull over national identity.

Exam Focus

• Typical question patterns:
  • Analyze how new technologies and mass media changed American society in the 1920s.
  • Evaluate cultural conflict in the 1920s using examples like Prohibition, the Scopes Trial, and the KKK.
  • Explain continuity and change from Progressive Era reform into the 1920s (what persisted, what shifted).
• Common mistakes:
  • Treating the 1920s as universally prosperous—remember farmers, many Black Americans, and many industrial workers did not benefit equally.
  • Describing Prohibition only as “people broke the law”—explain why reformers supported it and why enforcement failed.
  • Separating “culture” from “politics”—immigration restriction, Red Scare policing, and Klan influence show culture driving policy.

Immigration Policy and Nativism

Defining nativism and why it surged after World War I

Nativism is the belief that “native-born” Americans deserve priority and that immigrants are inherently threatening—economically, culturally, politically, or racially. Nativism is not just personal prejudice; it often becomes organized through lobbying, propaganda, and legislation.

Nativism surged in the years surrounding World War I for several connected reasons:

1. National security fears: Wartime suspicion of “foreign influence,” especially from countries the U.S. fought.
2. Economic anxiety: Competition for jobs and housing, especially during strikes and postwar adjustment.
3. Ideological fear: The First Red Scare encouraged Americans to associate immigrants with anarchism or communism.
4. Racial and religious prejudice: Many Americans viewed southern and eastern European immigrants (often Catholic or Jewish) as less “American” than earlier immigrants.

A common misconception is that restriction was only about economics. On APUSH, you should be ready to discuss how ideas about race, religion, and national identity shaped immigration law.

From openness to restriction: how immigration policy changed

Before the 1920s, the U.S. had already begun restricting immigration—especially targeting Asian immigrants—but the 1920s marked a major federal turn toward numeric limits.

Literacy tests and wartime restrictions

The Immigration Act of 1917 imposed a literacy test on immigrants and expanded categories of exclusion. Literacy tests were presented as “neutral” standards, but in practice they reduced immigration from poorer regions and reinforced class and ethnic bias.

Quotas: limiting immigration by numbers and by national origins

After World War I, Congress moved from qualitative restrictions (who is “undesirable”) to quantitative restrictions (how many can enter) and then to quotas based on nationality.

• Emergency Quota Act (1921): established numerical limits using national origin formulas tied to earlier census figures.
• Immigration Act of 1924 (Johnson-Reed Act): strengthened quotas and used national origins calculations that favored immigration from northern and western Europe while sharply limiting southern and eastern Europe. It also effectively barred immigration from Asia.

These laws mattered because they were not just “anti-immigrant”; they attempted to engineer the future ethnic composition of the United States.

Comparing key immigration laws (helpful for essays)

Nativism in society: organizations, trials, and “100 percent Americanism”

Nativism was expressed through both formal politics and social pressure.

The Ku Klux Klan and “Americanism”

The 1920s KKK wrapped intolerance in the language of “morality” and “patriotism.” This is important historically because it shows that discrimination often presents itself as defending national values rather than openly admitting prejudice.

Sacco and Vanzetti

The case of Sacco and Vanzetti (Italian immigrants and anarchists who were convicted of murder in the 1920s) became controversial because many believed they were treated unfairly due to their political beliefs and immigrant status. On exams, the case is often used as evidence of how Red Scare fears and nativism shaped policing and justice.

A common student mistake is to claim the case “proves” innocence or guilt. The safer APUSH move is to use it to demonstrate perceptions and bias in the era: many Americans believed radicalism and foreignness were linked, and the justice system was not immune to that climate.

Asian exclusion and the racial boundaries of citizenship

Long before 1924, the U.S. had restricted Asian immigration (for example, Chinese exclusion in the late 19th century). In the early 20th century, U.S. policy and court decisions continued to define citizenship in racialized terms. The broader pattern to understand: restrictions weren’t merely about numbers; they enforced a racial boundary around who could fully belong.

Mexican immigration and border enforcement in the 1920s

While the national-origins quota system focused heavily on Europe and Asia, migration from Mexico continued to matter due to labor demand—especially in agriculture and railroad work. In 1924, the federal government created the U.S. Border Patrol, reflecting a growing federal role in immigration enforcement.

It’s important not to oversimplify this into “Mexican immigration was unrestricted so there was no nativism.” In practice, discrimination and pressure could still be intense at the local level, and debates about labor needs vs. cultural fears were already present.

How immigration restriction connects back to World War I and the 1920s

Immigration policy is one of the clearest places where you can see the era’s themes converge:

• World War I expanded federal power and encouraged suspicion of dissent.
• The First Red Scare linked foreignness with radicalism.
• The 1920s culture wars encouraged “traditionalist” efforts to define America as white, Protestant, and “100 percent American.”
• Restriction laws translated those attitudes into long-lasting federal policy.

If you remember one big interpretive idea, make it this: immigration restriction was not a side issue—it was a central political outcome of postwar fear and 1920s identity conflict.

Exam Focus

• Typical question patterns:
  • Explain causes of immigration restriction in the 1920s (Red Scare, cultural conflict, racial ideology).
  • Compare immigration policies of the 1920s with earlier periods of migration and restriction.
  • Use a specific law (1917, 1921, 1924) as evidence in an argument about national identity.
• Common mistakes:
  • Saying quotas were only about job competition—include race, religion, and ideology.
  • Mixing up the sequence of laws—1917 literacy test, then 1921 quotas, then 1924 national origins system.
  • Treating nativism as only “social attitudes”—show how it became policy and enforcement (quotas, Border Patrol, trials, raids).