Kaplan is surely right to conclude from this that Beijing is unlikely to risk a military showdown involving Washington any time soon. Instead, he tells us — mixing historical analogies slightly — that China will “Finlandize” Southeast Asia. Confronted by the same kind of pressure that the Soviet Union applied to its Scandinavian neighbor during the Cold War, Southeast Asia’s governments “will maintain nominal independence but in the end abide by foreign policy rules set by Beijing.” Because Finlandization is so different from the way the United States threw Spain out of the Caribbean in 1898, the outcome will differ too. “But,” Kaplan concludes, “the age of simple American dominance, as it existed through all of the Cold War decades and immediately beyond, will likely have to pass. A more anxious, complicated world awaits us.”

These sentences might tempt readers to lump Kaplan into the company of “declinists,” writers who rejoice in announcing the imminent fall of the American Empire, but that would be too simple. ­Kaplan is in fact a leading proponent of the theory of international relations known as realism, which traces its ancestry back nearly 2,500 years to Thucydides. Kaplan is explicit about his intellectual debt to this tough-minded ancient Greek and, like him, glories in stripping away fondly held illusions to reveal the harsh reality of governments nakedly pursuing their own self-interest without concern for values, beliefs or ideology.

It is realism that keeps Kaplan’s book so refreshingly free of the breathless “oh my God it’s worse than you think” prose style that mars so much Western writing on the rise of China. In its place, however, realism encourages a Thucydidean detachment that some readers will find even more alarming. But that, Kaplan says, is the way it has to be, because the struggle over the South China Sea is going to be detached and unemotional. America’s struggle with the Soviet Union raised great moral issues and fired the passions of all involved; but it has proved hard to invest the South China Sea with the same philosophical freight as the Berlin Wall, despite the best efforts of some. (While writing a column for a newspaper — not this one — a few months ago, I was firmly informed that the editor wanted “less history, more scary stuff about China.”) “The fact is,” Kaplan observes, “East Asia is all about trade and business.”

The heroes in Kaplan’s story are hard, pragmatic men who recognize this, men like Singapore’s Lee Kuan Yew (“head and shoulders above most other leaders worldwide in the 20th century”) and China’s Deng Xiaoping (“one of the great men of the 20th century”). Realists to their core, both regularly turned on a dime, ditching what had once seemed to be deeply held convictions. Neither had much time for democracy; nor, it seems, does Kaplan. Admitting that such thoughts are “heretical to an enlightened Western mind,” he writes that “if you left the South China Sea issue to the experts and to the elites in the region, the various disputes would have a better chance of being solved than if you involved large populations in a democratic process, compromised as they are by their emotions.”

The solutions that would be reached, though, might not be the ones that most people around the South China Sea would want. In the course of his travels, Kaplan found the spirit of Lee and Deng much in evidence. One realist after another told him that they did not wish to be Finlandized or to replace America’s embrace with China’s; but realism teaches us that history is driven more by necessities than desires. “At the end of the day,” one Singaporean said, “it is all about military force and naval presence — it is not about passionate and well-meaning talk.” Since 2011, there has been much passionate American talk of a pivot toward Asia; but Vietnamese officials, realists to a man, respond by quoting a proverb — “A distant water can’t put out a nearby fire.”