The relationship between land and sea in human civilisation all through history has been determined at several levels. First of all, there is the geographical factor, largely though not entirely beyond the control of man. Technological knowledge and constraints, closely interwoven with social and cultural habits, constitute the second dimension. Lastly, the random elements of time, wars, famines, and the rise and fall of political empires, added their own imprints on the varying fortunes of ports, cities, merchant communities, and all those who stood to gain from long-distance maritime trade. How far the Indian Ocean made its influence felt in the vast sweep of land in the north and the south west, in the direction of Asia and Africa, is a fascinating question. The sea, of course, as Fernand Braudel has pointed out in another context, is not responsible for the sky that looks down on it. The global climate controlling the rhythm of seasons and the boundaries between aridity and dense vegetation was an autonomous phenomenon that played a vital part in forging the links between the Indian Ocean and the lands around it. Even in areas far beyond the immediate reach of the sea, as in the great chain of towns and cities that held together the Central Asian caravan trade, the pull of the maritime civilisations remained strong. The repeated migrations of nomads from the steppe towards China, the Middle East, and India are difficult to explain in terms of single or direct causation.