Many books end with a twist; in this one, the plot is described in its entirety in the first few chapters. On (Chinese) New Year's Day 1421, the Ming dynasty Emperor Zhu Di commanded a fleet of hundreds of Treasure Ships "to proceed all the way to the end of the Earth ... to attract all under heaven to be civilised in Confucian harmony". Some months later, Beijing and the Forbidden City was struck by a thunderstorm, deemed to be a bad omen, and over the following months and years China retreated into itself. The consequences of this were similar to those of the destruction of the library of Alexandria by the Christians: a population isolated, knowledge lost, documents destroyed. But Gavin Menzies' hypothesis is that the fleet embarked on a three year journey, in which it fragmented into four smaller fleets, that between them sailed to all the continents and circumnavigated the globe.
The bulk of the book describes the separate voyages of admirals Hong Bao, Zhou Wen, Zhou Man and Yang Qin, under the overall command of Zheng He. Some sections are more speculative than others; Menzies applies his knowledge, as a retired Royal Navy Commander, of astro-navigation and ocean currents, to suggest the likely courses and offers various evidence of Chinese visitations and settlement: maps available to the European powers before Henry the Navigator, Columbus, Magellan or Cook, inscribed standing stones, gifts of porcelain and silk, animal and plant populations, shipwrecks and so on. On a couple of occasions he takes pleasure in pointedly offering more terrestrial explanations of some artefacts than Eric von Daniken. As he draws to a close, he raises the question: why has no-one put this evidence together before? In part, perhaps, his seafaring knowledge has allowed him to make mental leaps that academics would not; and considerable sections in the appendix refer to DNA evidence that has been produced only recently. He notes that various Chinese academics have drawn similar conclusions; curiously it is in Australia and New Zealand where his hypothesis seems to have met with most opposition. Perhaps in post-colonial Europe and America, there is indifference to reopening history, written as it is by its apparent victors. Perhaps the politics of migration and globalisation plays its part today just as in 1421-3.
Rather like the Lord of The Rings, this epic struggles to conclude. There is a post script (part of which seems to be a post post script) describing the reception of some lectures Menzies gave from 2002 onwards, and two appendices: the first is a rather unstructured brain dump summarising the evidence; the second a much more interesting paper on the Chinese determination of longitude using lunar eclipses, demonstrated to be very accurate, though unlike Harrison's chronometers, completely impractical on a day-by-day basis unless one has a pre-calibrated map.
As a counterfactual, this is an entertaining book; but Menzies' presentation of the story makes it quite compelling, to the point where the greater surprise would be if the voyages of 1421 had not taken place. Mixing academia and mammon, he has produced a TV documentary, which I don't believe has aired in the UK, though it would certainly be interesting to watch; there is also a companion website.