1) "The military history of China extends from around 1500 BCE to the present day. China has the longest period of continuous development of military culture of any civilization in world history and had been the world's most advanced military for the longest time, from 200 BCE to the 16th century. Like the history of China, it is conventionally divided into three periods: ancient China (c. 1500-221 BCE), imperial China (221 BCE-1912 CE), and modern China (1912-present). Throughout most of the first two periods, the Chinese military was shaped by the military threats from the nomadic societies of Mongolia, Manchuria and central Asia, as well as legalism and later, the persistence of Confucian values. The third period relates to the efforts of the Chinese military to respond technologically and structurally to the West and Japan." "The barbarians of the northern frontier, commonly called hu (胡), include the nomadic Xiongnu, Turks, Khitan, Mongols. Others include the Xianbei and Jurchen, who combined nomadism with agriculture. All of these non-Chinese peoples were formidable because their male populations of military age were all warriors bred to the saddle and trained in the mounted archer mode of fighting that dominated Central Asia. Up until the modern age, the non-Chinese of the northern frontier were the only serious threat. Chinese responses to their periodic invasions were multi-faceted. One of the most obvious is the building of large-scale fortifications such as the Great Wall. Other strategies included the recruitment of ethnic Chinese cavalry, the recruitment of non-Chinese cavalry forces , and the use of diplomacy and trade to neutralise the hostile intent of the barbarians." Source and further information: http://en.wikipedia.org/wiki/Military_history_of_China 2) I found a very interesting article about this issue, here some excerpts: "Improving transportation technologies underlay cross-cultural interactions during the centuries between about 3500 and 2000 B.C.E. This first period of global history, the age of early complex societies, witnessed the establishment of sedentary agricultural societies in Mesopotamia, Egypt, India, and China. Yet these societies did not develop in isolation." "During this first age of global history, for example, migration and trade promoted the diffusion of horse domestication and bronze metallurgy, both of which influenced the development of states and societies from China to Egypt." "Stunning evidence of the eastern migrations has recently come to light in the form of desiccated but remarkably well-preserved corpses of Caucasian individuals unearthed in China's Xinjiang province.17 Indo-European migrants owed their mobility to their horses and wheeled vehicles, and they introduced their technologies of transportation to the lands they entered." "Improving technologies of transportation underwrote a noticeable expansion of cross-cultural trade during the age of ancient civilizations. China was too distant to trade directly with the other ancient civilizations, although nomadic peoples linked China indirectly to other Eurasian societies." "Migration and trade also facilitated cultural exchanges during the age of ancient civilizations. Chinese ruling elites of the Western Zhou dynasty (1027-771 B.C.E.) seem to have enlisted Persian magi as religious and ritual specialists." "A high point of cross-cultural interaction during classical times came with the elaboration of the intricate and well-articulated network of the so-called silk roads, both terrestrial and maritime." "Central Asian horses were crucial to Chinese military forces, and Chinese silks became essential apparel for fashionable women in Rome." "The early diffusions of Hinduism, Buddhism, and Christianity—not to mention the explosive expansion of Manichaeism—were processes that took excellent advantage of the trade routes of the classical era. [...] trade routes served not only as commercial and cultural highways but also as avenues for the dissemination of pathogens, which in turn caused destructive epidemics of disease." Source and further information: http://www.learner.org/channel/courses/worldhistory/support/whatis_reading_2.pdf