The Lao-Tai of the Yangtze Valley were evidently very numerous, for not only did they thus early establish kingdoms far from home but also became a power in their own land and for some time bid strongly for the mastery of all China. For centuries they waged successful wars on all their neighbors, but their strong propensity for wandering weakened their state and finally caused its disintegration. The Chinese attacked them repeatedly, each attack producing a fresh exodus until, during the thirteenth century A.D., the Emperor Kublai Khan dealt them a final blow which crushed their power and scattered them in all directions. Fugitives entered Assam, where earlier emigrants had already settled, and became the dominant power in that country; others invaded Burma, where for two centuries a Lao-Tai (Shan) dynasty occupied the throne; while down the Salwin and Me Khong Valleys came band after band of exiles who mingled with their cousins already established in those valleys and, in time fusing with the Mon and the Khmer, produced the race which, since the founding of the city of Ayuthia, has been dominant in Siam. The principal divisions of the Lao-Tai family now living within the borders of Siam are the Thai ("free men") or Siamese proper; the Lao, who occupy the former seats of those tribes of their own stock that afterward developed into the Thai; and the Shans, a later intrusion of distant cousins, descended from the Lao-Tai tribes that settled in the more eastern districts of Burma in the twelfth century and earlier. PREHISTORY The history of Siam prior to the fourteenth century A.D. is chiefly known from a hodgepodge of disconnected stories and fragments known as the "Pongsawadon Mu'ang Nu'a" ("Annals of the North Country"), compiled at different periods from such of the official records of various cities and kingdoms as had escaped the destruction which at intervals overtook the communities to which they referred. With the omission of the numerous supernatural happenings there recorded and comparative study of the chronicles of neighboring countries, scholars have been able to draw a rough picture of the condition of Siam at the dawn of historical time. Their researches show a country inhabited by primitive people of Mon-Khmer stock among whom had settled groups of their more civilized cousins from Cambodia, who had brought with them the religion and customs acquired by contact with colonists from India. These communities grew from villages into cities and at the same time sent out offshoots in all directions, which in time became the capitals of small states, the chiefs of which constantly made war on each other and against the Lao-Tai tribes at their borders and now and again rose to sufficient strength to repudiate the vague suzerainty claimed over them all by the empire of Cambodia.