AP Syllabus focus:
‘Compare how imperialism and global wars moved the United States into international leadership while renewing domestic debate over the nation’s proper role in the world.’
The United States’ global role from 1890 to 1945 transformed dramatically, shaped by imperial expansion, two world wars, and ongoing internal debates over power, democracy, and foreign engagement.
America’s Expanding International Role, 1890–1917
The closing of the frontier and rising industrial capacity encouraged policymakers to look outward. Many Americans argued that global competition required a more assertive presence in world affairs. Foreign policy decisions during this era often reflected tensions between imperial ambitions and republican ideals.
Imperialism and the Spanish–American War
U.S. imperialism accelerated in the late nineteenth century with the annexation of overseas territories. The Spanish–American War (1898) represented a pivotal moment when the nation embraced a more interventionist posture.
The acquisition of the Philippines, Puerto Rico, and Guam expanded U.S. influence in the Caribbean and Pacific.
Supporters of empire argued that global leadership required a strong navy, overseas markets, and strategic bases.
Critics insisted that empire violated principles of self-determination—the right of peoples to choose their own political status.
Self-determination: The principle that national groups should control their own political future rather than being governed by external powers.
These debates highlighted a recurring tension: whether the United States should act as a traditional imperial power or uphold democratic values even when inconvenient abroad.
Progressivism and Selective Intervention
During the Progressive Era, presidents such as Theodore Roosevelt and Woodrow Wilson pursued policies that blended moral rhetoric with strategic interests. Roosevelt’s Big Stick diplomacy and the construction of the Panama Canal confirmed U.S. regional dominance, while Wilson framed interventions in Latin America as efforts to promote democracy—a justification many contemporaries viewed skeptically.
World War I and Shifting Notions of Leadership
World War I intensified the question of America’s global responsibilities. Initially committed to neutrality, the Wilson administration eventually entered the conflict in 1917, claiming that U.S. participation would help make the world “safe for democracy.”
Wartime Decisions and Postwar Vision
American military involvement, though shorter than that of the European powers, allowed the United States to shape postwar diplomacy.
Wilson championed the League of Nations, asserting that collective security could prevent future wars.
Domestic critics feared surrendering national sovereignty to an international body.
The Senate’s refusal to ratify the Treaty of Versailles exposed the deep divide between internationalists and isolationists.
Isolationism: A foreign policy stance advocating limited political and military involvement in international affairs.
This 1919 political cartoon depicts the U.S. Senate confronted by an enormous “Peace Treaty” scroll, symbolizing the complexity and controversy of the Versailles settlement. The image underscores how many senators resisted U.S. membership in the League of Nations, reflecting powerful isolationist sentiment. It visually represents the domestic conflict over America’s proper role in global diplomacy. Source.
The failure to join the League underscored how global activism strained long-standing American suspicion of entangling alliances.
Interwar Years: Selective Engagement and Persistent Debate
Following World War I, Americans reassessed the country’s position in the global system. Many blamed international involvement for domestic instability, yet economic interests tied the nation to world markets.
Unilateralism and Avoidance of War
Throughout the 1920s and 1930s, U.S. policymakers favored unilateralism, meaning independent action without binding alliances.
Investments, naval conferences, and peace treaties aimed to stabilize global relations without military commitments.
The Neutrality Acts of the 1930s reflected widespread fears that economic ties could again draw the country into war.
Yet rising fascism in Europe and Japanese expansion in Asia forced Americans to reconsider whether neutrality was sustainable in a rapidly changing world.
World War II and the Emergence of Global Leadership
The attack on Pearl Harbor (1941) ended the neutrality debate and propelled the United States into a global conflict that would redefine its role permanently. The national response to total war accelerated diplomatic, military, and ideological commitments to broader international leadership.
Wartime Mobilization and International Cooperation
American industrial output and military coordination with Allied powers positioned the United States as the central force in defeating fascism.
New technologies, mass production, and unified military strategy elevated U.S. global stature.
The fight against totalitarianism reinforced the idea that the nation had a responsibility to defend democratic values worldwide.
Postwar Planning and the Foundations of Superpower Status
Even before victory, U.S. leaders shaped the postwar international order, influencing organizations like the United Nations and promoting open markets and political stability.
This United Nations photograph shows Edward R. Stettinius, Jr., signing the UN Charter in San Francisco in 1945 as President Harry S. Truman observes. The event marks U.S. leadership in shaping the postwar international order and establishing institutions for global cooperation. The page includes supplementary background about the conference beyond the AP curriculum, but the core moment directly illustrates America’s emerging superpower role. Source.
Europe and Asia emerged devastated, while the United States possessed unmatched economic and military power.
This imbalance ensured that the nation would enter the postwar world as a superpower, with expectations—both domestic and international—that it would assume a leadership role.
Continuities and Ongoing Debates, 1890–1945
Across this entire period, Americans confronted recurring questions:
Should the nation extend its influence to promote democracy or prioritize national security?
Does global leadership require military intervention or diplomatic engagement?
How can a republic committed to liberty justify empire, alliances, or global policing?
These debates intensified as U.S. power expanded, demonstrating that the rise to international leadership was accompanied by enduring disagreements over the nation’s proper place in world affairs.
FAQ
Public opinion often dictated how far policymakers were willing to expand U.S. influence abroad.
Support for overseas expansion surged briefly after the Spanish–American War, but scepticism about empire grew as Filipinos resisted American rule.
During World War I, propaganda and fears of radicalism shaped backing for intervention, yet disillusionment in the 1920s reinforced isolationist sentiment.
By 1941, rising awareness of global threats gradually shifted public attitudes, making support for intervention more politically feasible after Pearl Harbor.
Economic strength underpinned diplomatic leverage, military capability, and global influence.
Leaders believed access to foreign markets would sustain industrial growth and prevent domestic instability.
During both world wars, America’s productive capacity enabled it to supply allies and shape postwar arrangements.
Economic tools, such as loans and investment, allowed the United States to exert influence internationally even when avoiding formal alliances.
Racial beliefs shaped arguments for and against expansion.
Supporters of empire often claimed that non-white populations needed American guidance, using paternalistic logic to justify overseas control.
Opponents argued that governing diverse populations would undermine U.S. democratic principles and complicate racial politics at home.
These ideologies influenced attitudes toward immigration, colonial governance, and the nation’s perceived moral authority on the world stage.
Advances in communication and transportation made isolation increasingly impractical.
By the early twentieth century, faster shipping, telegraphy, and global news coverage made international developments harder to ignore.
During World War II, aviation and modern warfare demonstrated that physical distance no longer guaranteed security.
These shifts strengthened arguments that America needed a more active global role to protect its interests.
America’s decisive role in both world wars convinced many nations that U.S. involvement was essential to global stability.
Key expectations emerged because:
The United States held unmatched industrial and military power by 1945.
European and Asian devastation created a leadership vacuum.
American policymakers shaped key institutions, such as the United Nations, embedding U.S. leadership into the postwar order.
These conditions made sustained international engagement appear both necessary and inevitable.
Practice Questions
Question 1 (1–3 marks)
Identify one factor between 1890 and 1945 that contributed to the United States assuming a greater international leadership role, and briefly explain how it contributed.
Question 1
1 mark for identifying a valid factor (e.g., imperial expansion after the Spanish–American War, participation in World War I, industrial and military strength by 1945).
1 mark for a basic explanation of how the factor contributed to increased leadership (e.g., gaining territories expanded strategic influence).
1 mark for a more developed explanation showing clear linkage between the factor and the emergence of U.S. global leadership (e.g., World War II mobilisation positioned the United States as a superpower capable of shaping the postwar order).
Question 2 (4–6 marks)
Evaluate the extent to which debates within the United States over its proper international role shaped foreign policy decisions between 1890 and 1945. Use specific historical evidence to support your answer.
Question 2
1–2 marks for describing relevant debates (e.g., imperialism vs. anti-imperialism, isolationism vs. internationalism, concerns over sovereignty related to the League of Nations).
1–2 marks for providing accurate historical examples that show how these debates influenced policy (e.g., rejection of the Treaty of Versailles, Neutrality Acts, selective interventions in Latin America).
1–2 marks for demonstrating analytical judgement on the extent of influence, such as discussing continuity across decades or comparing the relative importance of domestic debate versus global pressures.
