THE POINT IS obvious but no less extraordinary for that: even though America is not of Asia, it has been the region’s hegemon for more than seven decades. Any change in its posture under Donald Trump might not be much noticed at home, but its implications in the region would be quickly felt.

America’s presence draws its justification, as Rana Mitter of Oxford university puts it, from the sacrifices made by American troops to recover the region from Japan during the second world war. Only North Korea challenges America’s claim to a legitimate presence there, and even in its hate-spewing rhetoric you can detect an admiration for the Americans.

The hard element of American power is embodied in the United States Pacific Command (PACOM), based in Hawaii and watching over what it calls the Indo-Asia-Pacific: a region from the Arabian Gulf in the west to the Galapagos Islands in the east, from northern Japan to the Southern Ocean, extending to 100m square miles (260m square kilometres) and 14 time zones. Power takes the form of military bases and listening posts strung out across the Pacific and Indian Oceans, from Alaska to South Korea to Australia to Diego Garcia.

As for East Asia, the Seventh Fleet, perhaps the world’s most powerful fighting unit, with over 60 ships, 140 aircraft and 40,000 sailors and marines, is based in Yokosuka, south of Tokyo. One-fifth of Okinawa, the main island of Japan’s southernmost archipelago, is given over to American forces. For the 28,500 American troops in South Korea, the demilitarised zone at the border with North Korea is the world’s last cold-war tripwire: one move across it by Kim Jong Un’s forces would meet with instant retribution.

Bruce Cumings of the University of Chicago refers to American power as a globe-girdling “archipelago of empire”, with most of America’s 800 bases in or near the Pacific. In Okinawa the American outposts have a whiff of strained cross-cultural relations about them: young, bored off-duty servicemen in customised pick-ups cruising the mall road, forlorn bars run by “Mama-san”, marriage counselling promoted on the forces’ television station. Yet supported by a huge and sophisticated defence industry back home, the archipelago still packs a punch. Last September the PACOM commander, Admiral Harry Harris, talking about American military hardware, boasted that “everything that’s new and cool is coming to the region,” including a new Zumwalt class of stealth destroyer straight out of “Star Trek”—and a Captain James Kirk as its commander to boot.

Extraordinary, too, how little changed is the structure of American power laid down for the region at the end of the war by General Douglas MacArthur, acting like an imperial viceroy. From the outset, Japan, South Korea and Taiwan—or at first, Chiang Kai-shek and his Kuomintang or Nationalists—became America’s main East Asian allies. Australia and New Zealand were the staunch English-speaking friends. All remain America’s key partners today. British, French, Portuguese and Dutch empires have crumbled. The Soviet Union has gone. Of the original threats in the region, only North Korea’s remains, and American forces are still there to contain it. Yet not just on the Korean peninsula but across Asia, America remains the indispensable power, a linchpin for regional stability, democracy and free trade.

East Asia’s stunning development path owed much to the nature of American power and of the region’s structure of alliances, producing economic successes that have never been matched elsewhere. The United States not only guaranteed the security of Japan, South Korea and Taiwan, allowing them to focus on economic development; it also provided them with the incalculable advantages of technical assistance, educational exchanges and nearly unfettered access to America’s vast markets. Crucially, it did not, at least initially, insist that these countries open their own markets in return.

Japan was the first to take off as its people swapped military uniforms for sarariman suits in pursuit of single-minded economic reconstruction. South Korea and Taiwan followed. They threw everything into building competitive export-oriented manufacturing bases, shutting foreign competitors out of their markets. Through what later came to be known as “financial repression”, they used capital controls, cheap exchange rates and subsidised loans to channel money into corporate investment and state infrastructure. By 1967 Japan was the world’s second-biggest economy. Only then did Japan’s partially closed markets become a growing bone of contention in America.

Arthur Kroeber, an expert on the Chinese economy (and a former contributor to The Economist), points out that American power profoundly shaped these East Asian allies in another respect: the nature of their politics. Over time, the need for their patron’s approval forced them to adopt democratically accountable political systems. Japan’s was foisted on it by its American occupiers. On Taiwan, Chiang Kai-shek’s son, Chiang Ching-kuo, started moving the island towards representative politics in the 1980s in response to the shock of America normalising its relations with Communist China. In South Korea, America put up with military dictatorship during the cold war, but probably would not have tolerated it after the fall of the Berlin Wall. As it happened, protests leading up to the 1988 Olympics in Seoul ushered in the restoration of civil liberties and direct presidential elections. Today all three countries are among Asia’s staunchest democracies.

The Chinese policeman

What was not expected at the outset was China’s withdrawal from the post-war Asian order. During the war Chiang Kai-shek’s Kuomintang forces had not defeated the Japanese, but for eight long years they had bravely tied down Japanese armies in China, at the cost of 14m Chinese dead. That made China an American ally and a victor. Franklin Roosevelt wanted it to take its place as a sovereign power, one of the world’s “four policemen”, as he put it. He, Chiang Kai-shek and Winston Churchill had met in Cairo in 1943 to make this happen. What no one had counted on was that China’s Communists under Mao Zedong would use the Nationalists’ war exhaustion and growing popular disenchantment to rekindle a smouldering civil war in which they swept to victory in 1949. The following year, far from being an ally, China was fighting against America on the Korean peninsula (where Mao’s own son was killed in battle). It took two decades for China to come out of its shell when America’s then president, Richard Nixon, paid a visit to Beijing.

The ground for China’s opening to America was prepared by a rupture in its relations with the Soviet Union in 1960. For over four decades it has been an unambiguous beneficiary of the American order. Without America to keep its neighbourhood secure and underpin open markets, China could not have reaped such gains from the market-led reforms it launched in the late 1970s. It benefited from being geographically close to the economic dynamism and the distribution networks of the East Asian tigers. Lacking the American allies’ access to Western markets, management and technology, China threw itself open to foreign investment—a remarkably pragmatic surrender of economic sovereignty. But now that China has become richer and more powerful, its aspirations to regional leadership and even hegemony are growing stronger. After all, it, too, won the war.