Monsoon melds two very different books into one. One book is a geopolitical treatise, conceived on a grand oceanic scale. It argues that global power shifts mean the Indian Ocean is becoming again the fulcrum of world power and will be the main theatre of strategic rivalry in the twenty-first century. The other book is a travelogue that takes the reader on an excursion around the Indian Ocean’s rim, offering an engaging mix of potted history, contemporary politics and intriguing encounters in some of the world’s most interesting places.

The mix of travel and strategy works because Kaplan is a good writer, and his strategic ideas have always been infused with a sense of adventure. He is a kind of Rudyard Kipling of the American Empire, exploring and explaining the points, far from Washington, where American power actually meets the disorderly world it seeks to contain. And like Kipling, he loves the dramatis personae of the empire, the proconsuls and the foot soldiers who manage its frontiers, and the colourful characters and strange places they encounter.

Kaplan gives us plenty of this. Not just Vasco da Gama, but Camões and The Lusíads, Curzon in Calcutta, Clive winning India for Britain at Plassey, and Coen building Batavia. He sketches today’s events in Yemen, Oman, Pakistan, India, Bangladesh, Burma, Indonesia and Zanzibar in fine style. And he paints engaging portraits of people – Gujarat’s creepy chief minster; Indonesia’s enigmatic Gus Dur; and the strange American activists, the children of missionaries, who hover on the margins of Burma. All good stuff, but the travelogue is not the better part of Monsoon. Nor is the geopolitical argument particularly compelling in itself. But the thesis about the Indian Ocean becoming the centre of world politics is not really the focus of the book; its heart is a reflection on the future of American global power. In the past, Kaplan has been among those who most eagerly promoted and celebrated the US’s place at the pinnacle of world power in the twenty-first century. This new book strikes a very different note. From the epigraph, quoting Samuel Huntington on the West’s relative decline, to the book’s oddly elegiac last line about how best to preserve American power in a world it no longer dominates, Monsoon’s subtext is the waning of the US and the rise of China. Kaplan’s account of China’s rise is sophisticated and his sense of America’s response is nuanced. This is a very different view from the one Kaplan offered in pieces such as ‘How We Would Fight China’, published in the Atlantic Monthly only a few years ago.

Monsoon is an early sign that, quite suddenly, something is changing in the way the US sees its place in the world. Here too, Kaplan echoes Kipling, and Monsoon puts you in mind of the line from his poem

‘Recessional’: “Far-called, our navies melt away.” Kipling warned his countrymen of potent facts they preferred to ignore. If Kaplan’s book helps Americans – and America’s friends – to think more deeply about their role in the world, it could be a very important book indeed.