climate and geography: Asia and the Pacific 225 disastrous flooding than those that watered early civilizations in the Near East and India As a consequence, from very early times large-scale centralized government was necessary in China to deal with the maintenance of the water system, including dams, dikes, and canals The scale and efficiency of these works reached their height in the Middle Ages under the Sung (960–1279 c.e.) and Yuan (1279–1368) dynasties These works included the Grand Canal, a network of artificial inland waterways more than 11,000 miles long connecting central and northern China and allowing barge traffic to move at right angles to China’s generally eastward-flowing river systems Korea is a peninsula divided from the Chinese mainland by the Yalu River It is mountainous, though few of the peaks reach 6,500 feet Because of its position, it was inevitably influenced culturally and politically by China and, in turn, developed in interaction with Japan Because Korea was characterized by smaller, distant river valleys separated by mountains, during the Middle Ages it was divided among several states usually at war with one another Imperial Tang (618–907) and Sung China alternated tactics of diplomacy with military intervention against the smaller-scale and more vulnerable Korean states, but in 1231 the Mongols conquered Korea outright Located just off the Korean coastline, the islands of the Japan archipelago are separated from mainland Asia by the Sea of Japan While more than 3,000 islands are in this group, the main islands are (from south to north) Kyushu, Shikoku, Honshu, Hokkaido, and Sakhalin The most southerly three of these islands are the core areas for the emergence of rice agriculture about 1000 b.c.e and the first Japanese states around the fourth through the seventh centuries of the Common Era, with earlier hunting-andgathering populations known as Jomon peoples pushing northward into northern Hokkaido by around the seventh century c.e The islands of Japan are volcanic and extremely mountainous They are also subject to frequent powerful earthquakes with attendant landslides, making much of the land unsuitable for farming even though the climate is temperate As a result, throughout the medieval period most of the mountainous land area was forested and remains so today, but the limited lowland alluvial plains were used intensively for wet-rice agriculture, allowing the population to grow dramatically in the early kingdoms and through the medieval shogunate period Japanese culture has been deeply influenced by that of China Isolated by an arm of the Pacific Ocean, however, Japan did not fall under the political domination of China in the Middle Ages The Mongol Empire sent invasion fleets to Japan in 1274 and 1281, but both were repelled, at least partly because of severe damage to attacking Mongol ships from two of the typhoons typical of the weather in that area India The Indian Subcontinent, consisting of the modern countries of India, Pakistan, Bangladesh, and Sri Lanka on the island of Ceylon, surrounded by the Indian Ocean, is cut off from the rest of Asia by a ring of the world’s highest mountains: the Hindu Kush, the Karakoram range, and the Himalayas These mountain ranges contain peaks such as Mount Everest (29,030 feet) in the Himalayas and K-2 (28,250 feet) in the Karakoram, the highest and second-highest mountains in the world, respectively These ranges have generally protected India from invasion from inner Asia since prehistoric times, except for the invasion of the Mongols begun by Tamerlane in the late 14th century Runoff from these mountains feeds two great rivers in the northern plain of India: the Indus (home to one of the earliest centers of civilization), emptying into the Arabian Sea, and the Ganges, emptying through a massive delta of mangrove swamps in Bangladesh into the Bay of Bengal South of these river valleys most of India is taken up by the mountainous territory of the Malwa, Deccan, and Chota Nagpur plateaus To the west of the Indus Valley lies the Thar Desert Protected from most cold fronts moving from the north by its encircling mountains, India is far hotter than other areas of the world lying at the same latitude In the summer months (March through June), the average temperature on the Gangetic plain (where the bulk of the population lived in the Middle Ages as in modern times) is 104 degrees Fahrenheit Given these conditions, droughts are quite common Nearly the entire year’s rainfall is concentrated in the monsoon or rainy season (June through September) At this time a series of storms moving from west to east breaks over the subcontinent from the Arabian Sea Aside from making agriculture practical, if relatively uncertain, in India the monsoon has had an important effect on world history The prevailing winds during the monsoon season made it unusually easy for sail-powered ships leaving the mouth of the Red Sea (between Africa and Arabia) to travel directly to the island of Ceylon, laying off the southeast tip of the Indian Subcontinent just above the equator Once the monsoon was over, the return trip from Ceylon to the Red Sea was made just as easily on the winds blowing back to the west of the so-called retreating monsoon This exceptional condition made the voyage possible for ancient and medieval ships that otherwise rarely left sight of land because they lacked even rudimentary navigational technology like the compass This weather system was first systematically exploited for trade in antiquity by the Ptolemies