There is dispute as to the movements of the Tai-speaking peoples to the area they now occupy. According to tradition, the Tai Lue entered this area and displaced earlier inhabitants, who included the modern-day Akha, in about the eighth and ninth centuries. No evidence is available to verify these claims. Tai came into contact with the Han in the fourteenth century. Nineteenth-century European scholars suggested that the kingdom of Nan Chao (seventh to thirteenth century) was Tai. This view is now generally rejected. Tai speakers probably formed only a small, nondominant section of the population. Under the Mongol Yuan dynasty, Yunnan was incorporated into China, but control was little more than nominal until 1325 when a Lue chieftain was appointed Chinese commander-in-chief based in Jing Hong. Suzerainty over Sipsongpanna fluctuated among the Ming emperors (fourteenth to seventeenth centuries), local rule, and the Toungoo dynasty of Burma. Ming control of Sipsongpanna was greater than that of the Mongols. They interfered with the hereditary succession of Lue chiefs and demanded silver tribute. Ming control was extended to the Mekong River and was mainly peaceful to the middle of the seventeenth century. The conquest and pacification of the southeastern region proceeded with much turbulence during the eighteenth and nineteenth centuries. The prizes sought were the region's tea and cotton. During the middle years of the nineteenth century much of Sipsongpanna was in revolt against Chinese attempts to impose land taxes and remove the powers of the Lue chieftains. In many parts of the country the outcome was joint authority vested in Chinese magistrates and Tai chiefs. The chief of Jing Hong was recognized as suzerain over the chiefdoms, which constituted the twelve panna. He had the title of cawphaendin, which is translated as "king." During World War II Yunnan suffered badly in the conflict between the Allies and the Japanese. Siam was then occupied and an ally of the Japanese, and Sipsongpanna was subject to rather indiscriminate bombing because of the alleged presence of Chinese troops. Many Lue fled to Burma and northern Thailand at this time. With the victory of the Communists and the establishment of a Communist administration in Sipsongpanna, the kingdom ceased to exist: the last king is now an academic in Kunming. There was much movement out of Sipsongpanna. Among the nobility and elite many Tai had thrown in their lot with the Kuomintang and so most fled to Taiwan. There were divisions within the court on purely factional lines and this determined, to some extent, who stayed and who fled. Many, including both nobility and common people, also fled to Burma and Thailand. During the hundreds of years that Chinese rule was being extended into Sipsongpanna, the region and the Lue also had cultural links, political alliances, and conflicts with Tai speakers in Burma, Thailand, and Laos. Sharing very similar languages with these peoples, the Lue developed similar forms of Theravada Buddhism, a common literary tradition, and much familial contact. The twentieth century has seen these lessen, although contacts improved during the 1980s. There has been much recent movement of population between China, Myanmar, and Thailand. At the elite level this movement has been by air between Bangkok and Kunming, but there is also a probably more important movement of ordinary people, by foot, motorcycle, boat, and pack animal. The reasons for this movement include trade, family visits, religious purposes, and professional pursuits.