The cheers greeting Theodore Roosevelt on his triumphant return from a few days of battle in Cuba in summer 1898 were as much for America itself as for him. The swift, predictable defeat of Spanish forces confirmed what had been evident for decades, namely, that the United States would be among the dominant powers of the 20th century. Roosevelt’s charge up San Juan Hill with his Rough Riders may have been a modest contribution to the American victory, but it was symbolic of the ferocious, unrestrained energy that the U.S. promised to bring to the world.

The Spanish-American War came just five years after historian Frederick Jackson Turner penned his famous essay on the closing of the American frontier. Jackson’s thesis—that centuries of American expansion had come to an end with the full settling of the American continent—seemed perhaps even more important culturally, in terms of the country’s long-standing image of itself as a pioneer nation, than it did in a political and economic sense. But if America indeed had run out of continent to settle, it would soon prove itself an expansionist nation still, only its manifest destiny would henceforth radiate outward, and in particular into the vast Pacific in a seamless flow from the now-pacified American West. A clear sign of this national feeling was the adulation accorded to Commodore George Dewey, whose destruction of the Spanish fleet in Manila Bay on May 1 not only opened hostilities with Spain but announced unmistakably America’s ability to dispatch its military force halfway around the world.

The Spanish Philippines, of course, had never been coveted by America. On the other side of the Pacific, they were too isolated from the U.S. mainland to be of serious interest. Even Abraham Lincoln’s secretary of state, William Seward, had ignored the Philippines in his rhetoric that portrayed the Pacific as a “great highway” for American trade to Asia. Spanish Cuba, on the other hand, had for decades been a major part of the American political debate, first as a potential target for acquisition by antebellum slaveholders in the South, and afterwards as a moral cause when indigenous independence movements were brutally suppressed by the Spanish government. Cuba’s Ten Years’ War, from 1868 to 1878, was followed in 1895 by the War of Independence, in which at least 200,000 Cubans died when herded into concentration camps under the orders of Spanish general and governor Valeriano Weyler. Publicity in the United States of Spanish atrocities made a cause célèbre, and pushed President William McKinley into sending the U.S.S. Maine on its ill-fated mission to protect American property in Havana in early 1898 in the midst of uprisings against a new, autonomous colonial government. Though revenge for the (probably accidental) explosion and sinking of the Maine drove U.S. public opinion in favor of war in Cuba, Assistant Secretary of the Navy Theodore Roosevelt took advantage of the run up to hostilities to issue orders to Commodore George Dewey to prepare to destroy the Spanish fleet in Manila Bay. On May 1, 1898, before any significant combat action in Cuba, Dewey’s squadron destroyed the Spanish and plunged America on the road to colonialism.

In less than three months the spoils of the Spanish-American War, combined with the annexation of Hawaii, presented America with an empire—modest in size compared to the massive holdings of the British or French, but one that placed 11 million people from the Philippines, Cuba, Hawaii, Puerto Rico, and Guam (and soon Samoa) under U.S. control. The events of 1898 were as decisive in their own way as the American Revolution, the Civil War, and, later, the two world wars.

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The magnitude of America’s inauguration as an imperial power was not lost on observers at the time or since. A small cottage industry of historians has steadily churned out volumes over the past century on the significance of 1898. None disputes the importance of the moment; rather, the debate is over what led to it. Was American overseas expansion pushed by a cabal of aggressive imperialists, or was it an empire acquired absentmindedly? Is our tradition mainly to build a virtuous society at home, or to “set out into a sinful world and redeem it,” as Stephen Kinzer puts it in his new book, The True Flag: Theodore Roosevelt, Mark Twain, and the Birth of American Empire?

The dominant understanding of these events was set by the dean of American diplomatic scholars, Samuel Flagg Bemis, whose landmark work, A Diplomatic History of the United States, published in 1936, included a chapter entitled “The Great Aberration of 1898.” The same year, Julius W. Pratt’s Expansionists of 1898, which focused in particular on the question of annexing Hawaii, emphasized the steady shift from imperial hesitation to imperial advocacy by business and religious leaders, and finally by President William McKinley and his inner circle. Two decades later, Howard K. Beale, in Theodore Roosevelt and the Rise of America to World Power (1956), came out even more strongly for what might be labeled the “conscious disruption” thesis: that T.R.’s will to power in the international arena marked an abrupt transition from America’s traditional approach, even if the new policy was conditioned by shifts in late 19th-century global power. This view of 1898 as a consciously adopted radical change in U.S. policy has retained its appeal, and can be found in Walter McDougall’s Promised Land, Crusader State (1997), Warren Zimmerman’s First Great Triumph (2002), and other books.

Other scholars have offered a different interpretation. Among them, Harvard’s Ernest May argued in his 1961 study, Imperial Democracy: The Emergence of America as a Great Power, that “in the 1890s the United States had not sought a new role in the world.” In May’s view, foreign issues—including Hawaii and Cuba—had “intruded almost of their own accord” into the consciousness of policymakers who were concerned almost exclusively with domestic concerns. “Some nations achieve greatness,” May memorably concluded, “the United States had greatness thrust upon it.” And from an entirely different position, Robert Kagan, in his Dangerous Nation (2007), also disagreed that 1898 marked anything different in U.S. foreign policy: America from the beginning had been a state driven to conform the world to its radical vision of liberty.

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Stephen Kinzer, a former New York Times correspondent who has written several books on America’s involvement in South America and the Middle East, could not disagree more, not only about how America achieved its global position, but about whether that position constitutes “greatness.” Into this already crowded field, which includes H.W. Brands’s Bound to Empire (1992) and Evan Thomas’s The War Lovers (2010), among others, Kinzer offers another look at the imperial moment, one focused less on the mechanics of empire creation and more on the domestic debate surrounding it, a timely approach given the bitter debates since 9/11 over America’s role in the world.

Although Kinzer focuses on Teddy Roosevelt’s aggressive imperialism, he acknowledges that the desire for overseas glory was widespread. The American people and their representatives supported the new global role, though imperialist policy was at times a near-run thing. If there is a moment of high drama in Kinzer’s account, it is the ratification of the Treaty of Paris, which ended the war with Spain and confirmed the taking of the Philippines. Seemingly doomed to defeat in the Senate, the treaty was saved when William Jennings Bryan inexplicably withdrew his opposition and argued in favor of annexation, due in part to belief that it was the surest way to get independence for the Filipinos, and in part due to political calculations that a defeat of the treaty would be held against him in the coming presidential election. Despite such strategizing, Bryan again played a major role in ensuring what might be called the “settlement of 1898”—this time by losing the election of 1900, thereby saving McKinley’s imperialist course from reversal.

This is not newly plowed ground, and even if it were, Kinzer’s narrative shows that there really wasn’t that much to the debate. Despite the subtitle, Mark Twain shows up only near the end of the book, while the bulk of the tale turns on congressional debates over annexation, war, and peace treaties, and on the unsuccessful activities of the American Anti-Imperialist League. Less detailed than Beale’s or Zimmerman’s accounts, Kinzer’s book relies heavily on economic explanations for expansion while downplaying serious strategic arguments.

At times judgmental and flippant, he really comes out swinging in his final chapter, “The Deep Hurt.” Galloping through the subsequent century of American involvement in the world, he links Manila Bay to the Bay of Pigs, the Battle of Santiago to Baghdad, and so on. America got hooked on interventionism in 1898, Kinzer argues, and has never been able to kick the habit, despite repeatedly getting burned in the process. “Violent intervention in other countries always produces unintended consequences,” he solemnly intones. Well, yes, but that doesn’t help in figuring out precisely where and when we do need to intervene abroad, and his assertion that “we cannot agree…what foreign policies truly are in our interest,” simplifies far too much.

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Like America in 1898, we stand today at a crossroads, but a different one. How far to withdraw from the world is our debate today, not how far to plunge in. Few are the voices after Iraq that call for American boots on the ground anywhere and at any time. The current disorder abroad doesn’t require such profligate intervention, nor is a war-weary American public willing to support it. Yet equally unrealistic are the demands to pull up the drawbridges and ignore threats to our interests, particularly in strategic regions of the world.

As Beale and Zimmerman demonstrated, once Theodore Roosevelt swallowed his first big imperial meals, he refrained from further gluttony. Perhaps 1898 should be viewed as the opening act of a strategy that ultimately found an equilibrium. Recovering that equilibrium—recognizing that involvement in the world provides both benefit and danger—is the real challenge we face.