EURASIA is back. Ever since the publication of Halford Mackinder’s famous 1904 essay, “The Geographical Pivot of History”, military-minded schoolboys have fantasised about the possibility of a Eurasian empire stretching (in the much more recent words of Vladimir Putin) “from Lisbon to Vladivostok”. Mackinder was perhaps the most influential geographer of his day, and he reckoned Central Asia’s “potentialities in population, wheat, cotton, fuel, and metals so incalculably great, that it is inevitable that a vast economic world, more or less apart, will there develop inaccessible to oceanic commerce”. He forecast that by the end of the twentieth century, Central…