Mainstream media tends to understand China's strong grip on Tibet as a function of China's communist preference for authoritarian rule, driven by intangible factors like nationalism or Han chauvinism. Although these factors are indeed in play, they give an incomplete understanding of why Tibet is important to China. History suggests that China's need to control Tibet is geopolitical and not unique to any single Chinese government or to Han rule. The Tang Dynasty (618-907), the Manchu-ruled Qing Dynasty (1645-1911) and the Nationalist government (1927-1949) all fought to either dominate or pacify Tibet.
The Tang Dynasty was a cosmopolitan golden age for China's culture and arts, as well as a high point of Chinese military and economic might. At that time, China's center of gravity was not on its eastern seaboard as it is today but in northwestern China in what is modern Shaanxi Province. However, another power challenged China's control of the western frontier: the Tang Dynasty's most powerful foe, the Tibetan Empire. The two empires fought frequent wars between the early seventh century and the mid-ninth century to dominate the Silk Road, a network of trade routes running westward from the Tang capital Chang'an (modern Xian) through Central Asia, Persia and Europe.
At the height of the Tang Dynasty, its conflict with the Tibetan Empire was one for economic advantage, not a fight for survival. However, when the power of the dynasty's central government deteriorated, Tibet became a threat to the Chinese heartland. To check the Tibetans, the Chinese restructured their military from a system concentrating military power in the capital to a system of frontier commands with enormous standing armies, shifting the balance of power from the central government to regional commanders.
Although China's struggle against Tibet was most intense in the Tang Dynasty, subsequent Chinese governments saw the conflict as an indication of China's need to bind the Tibetan Plateau to the central government's will. Today, changes in military and logistics technologies have eroded the geographic advantage the Tibetans enjoyed in the past, enabling the Chinese to control Tibet to a degree unimaginable to their Tang Dynasty predecessors. But while it is extremely doubtful that Tibet could secede from China and quickly become a military power capable of capturing territory from the Chinese, Tibet is still geographically well-positioned to disrupt China's overland trade routes. And given its history, China has good reason to be anxious about a Tibetan challenge to its power. What outsiders might call a heavy-handed approach to governing the region, the Chinese government might simply call a necessity.