Between the end of the 19th century and the outbreak of World War I, Americans were forced to confront a major question: What role should the United States play in the world? As the country grew more powerful economically and militarily, debates over imperialism, global responsibility, and national identity sharpened. Should the U.S. use its power to expand and influence other nations, or should it resist the pull of empire and focus on domestic concerns? From the Spanish-American War to the brink of war in Europe, Americans fiercely disagreed over what kind of world power the nation should become.
Arguments for Expansion
Supporters of U.S. expansion believed that a stronger presence abroad would ensure national security, economic opportunity, and global leadership. One of the most influential voices in this camp was Alfred Thayer Mahan, a naval officer and historian. In his book The Influence of Sea Power upon History, Mahan argued that great nations were built on strong navies and overseas bases. To remain competitive, the United States needed to acquire territories, modernize its navy, and secure access to global trade routes.
This idea was echoed by Josiah Strong, a Protestant minister who saw expansion in moral and religious terms. Strong believed that the United States had a divine responsibility to “civilize” and Christianize other parts of the world. His vision of imperialism was rooted in ideas of racial and cultural superiority, reflecting the broader belief in American exceptionalism.
Frederick Jackson Turner, a historian, offered another rationale. In his famous “Frontier Thesis,” Turner argued that the American identity had been shaped by westward expansion. With the western frontier declared closed by 1890, he suggested that new frontiers—overseas—were essential to maintaining the nation’s democratic spirit and sense of purpose.
These thinkers helped justify American actions in the Spanish-American War (1898), in which the U.S. defeated Spain and acquired territories like Puerto Rico, Guam, and the Philippines. Expansionists celebrated these gains as proof that the U.S. was becoming a global power.
Voices of Opposition
At the same time, a growing group of Americans opposed imperialism on political, moral, and practical grounds. Anna Julia Cooper, a Black feminist scholar and educator, challenged the hypocrisy of American expansion. How could the U.S. claim to bring freedom and civilization to others while denying basic rights to Black Americans, women, and Indigenous people at home? Cooper’s writing emphasized that true progress required justice and equality—not domination.
Jane Addams, a social reformer and peace activist, added a democratic critique. She warned that imperialism eroded democratic values by promoting violence, racial superiority, and the subjugation of others. Addams argued that foreign policy should reflect the same values of cooperation and fairness that reformers were trying to build within the United States. She also warned that interfering in other nations’ affairs without their consent threatened the sovereignty of those peoples—their right to govern themselves without foreign control.
These anti-imperialist voices found support in organizations like the American Anti-Imperialist League, which included prominent figures such as Mark Twain and former President Grover Cleveland. They opposed U.S. control of the Philippines and warned that empire would compromise American ideals.
The Question of War: Preparedness vs. Neutrality
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As war broke out in Europe in 1914, these debates shifted from expansionism to a new question: Should the United States enter the war? President Woodrow Wilson initially declared neutrality, reflecting the views of many Americans who were wary of foreign entanglements.
Neutrality, however, did not mean indifference. While the U.S. stayed out of combat, it increased trade with Allied nations and debated how to prepare for a possible entry into war.
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Supporters of preparedness argued that the U.S. needed to build its military strength to protect its interests and influence the postwar world. Business leaders and politicians feared that if the U.S. remained passive, it would be shut out of global decisions and economic opportunities. They also believed that a show of strength might deter attacks and secure peace through power.
On the other side, neutralists warned that military buildup would drag the U.S. into a war that did not serve its interests. Many feared that joining the war would divide the nation, especially among immigrant communities with ties to Europe. Others, including pacifists and progressives like Addams, saw war as a betrayal of the values of peace, reform, and diplomacy.
The preparedness vs. neutrality debate echoed earlier disputes over expansion: Should the U.S. lead through strength and action, or through restraint and principle?
These early 20th-century debates about expansion and global responsibility reveal deep questions about American identity and purpose. Whether supporting military buildup or calling for peace, pushing for empire or defending democracy, Americans were negotiating the values that would shape their role in the world. As the country edged closer to involvement in World War I, those divisions remained unresolved—reflecting a nation still struggling to define the balance between power and principle.