The Spanish-American War was described by Secretary of State John Hay as "a splendid little war; begun with the highest motives, carried on with magnificent intelligence and spirit, favored by that Fortune which loves the brave." When the war began, little thought was given, at least publicly, to the possibility of an American empire. Yet no sooner had American forces begun to win victories over the Spanish than calls for annexations became widespread. The Treaty of Paris, which officially ended the war on 10 December 1898, recognized eventual Cuban independence, but provided for the cession to the United States of Spain's other colonies in the Philippines, Puerto Rico, and Guam. What ensued was a protracted and bloody struggle for control of the Philippines that caused many Americans, known as the "anti-imperialists," to openly question the annexation policy.
The great debate over American overseas expansion saw the two main strands of exceptionalist belief come into direct conflict with one another. Americans on both sides of the imperialism debate utilized arguments based on their beliefs about the exceptional nature of the United States. They did so even when they recognized what they regarded as legitimate economic, strategic, political, racial, or constitutional reasons for or against the annexation of overseas territories.
The commercial and strategic advantages of annexation provided the rationale for most expansionists. Yet many expansionists also expressed their conviction that annexation was a morally acceptable policy because it was the duty of the United States, as God's emissary, to extend freedom and democracy whenever possible. It was their divine destiny that called the Americans to free Cuba, the Philippines, Puerto Rico, and Guam from the grip of Old World imperialism. They believed it was the special duty of the United States to help those people overcome oppression and guide them toward the light of the principles of liberty and freedom. The expansionists frequently argued that America was not simply imposing its own brand of Old World imperialism. Rather, they argued, it was adopting these childlike nations so they could be nurtured to maturity and statehood. In time, once they were ready, these nations could choose for themselves whether to be independent or join the Union. The imperialists, drawing upon the tradition of manifest destiny, were strong believers in and advocates of the missionary strand of American exceptionalism.
The anti-imperialists, on the other hand, had a different view of the special American role in the world that reflected the exemplar strand of exceptionalism. They were more concerned that, having ousted the Spanish, the United States should leave the liberated states to determine their own destinies, in keeping with the American dedication to the idea that governments derive their power from the consent of the governed. The anti-imperialists emphasized the aspects of exceptionalism that regard the United States as being above the meddling immorality of Old World imperialists. They argued that the United States is special because it does not involve itself in the affairs of others, particularly not a nation on the far side of the Pacific Ocean that could hardly be considered within the U.S. geographic sphere of influence. As Charles Eliot Norton made clear, he and his fellow anti-imperialists believed that the transformation of the United States into an imperial power "sounded the close of the America exceptionally blessed among the nations." The anti-imperialists aimed to preserve the exceptionalist nature of the U.S. by preventing Americans from seeking dominion over other peoples in the way that other world powers did. As well as moral arguments, they also gave political, economic, constitutional, diplomatic, racial, and historical reasons for their opposition to annexations. But although their individual opposition varied, the essence of their protest was that they feared the United States was acting in a manner inconsistent with the principles laid down by the Founders. Thus both imperialists and anti-imperialists believed they were arguing for conduct consistent with the idea that the United States was an exceptional nation with a special role to play in human history. They both agreed that the U.S. was different from—indeed, better than—other nations; where they disagreed was on the precise nature of that exceptionalism.