The early Ming emperors held Mongol fighting men in awe and feared they might form another great military machine of the sort Chinggis Khan (ca. 1162–1227) had put together two centuries earlier. Although in Ming times the Mongols were never united in a pan-Mongol federation, groups of Mongols could and did raid. Twice they threatened the dynasty: in 1449 the khan of the western Mongols captured the Chinese emperor, and in 1550 Beijing was surrounded by the forces of the khan of the Mongols in Inner Mongolia. Fearful of anything that might strengthen the Mongols, Ming officials were reluctant to grant any privileges to Mongol leaders, such as trading posts along the borders. Instead they wanted the different groups of Mongols to trade only through the formal tribute system. When trade was finally liberalized in 1570, friction was reduced.

Two important developments shaped Ming-Mongol relations: the construction of the Great Wall, and closer relations between Mongolia and Tibet. The Great Wall, much of which survives today, was built as a compromise when Ming officials could agree on no other way to manage the Mongol threat. The wall extends about 1,500 miles from northeast of Beijing into Gansu province. In the eastern 500 miles, the wall averages about 35 feet high and 20 feet across, with lookout towers every half mile. Much of the way, the wall is faced with brick, which gives it an imposing appearance that greatly impressed the first Westerners who saw it.

Whether the wall did much to protect Ming China from the Mongols is still debated. Perhaps of more significance was the spread of Tibetan Buddhism among the Mongols. Tibet in this period was largely ruled by the major Buddhist monasteries. When Tibetan monasteries needed military assistance, they asked competing Mongol leaders for help, and many struggles were decided by Mongol military intervention. The Tibetan Buddhist Tsong-kha-pa (1357–1419) founded the Yellow Hat, or Gelug-pa, sect, whose heads later became known as the Dalai Lamas. In 1577 the third Dalai Lama accepted the invitation of Altan Khan to visit Mongolia, and the khan declared Tibetan Buddhism to be the official religion of all the Mongols. The Dalai Lama gave the khan the title “King of Religion,” and the khan swore that the Mongols would renounce blood sacrifice. When the third Dalai Lama’s reincarnation was found to be the great-grandson of Altan Khan, the ties between Tibet and Mongolia, not surprisingly, became even stronger. From the perspective of Ming China, the growing influence of Buddhism among the Mongols seemed a positive development, as Buddhist emphasis on nonviolence was expected to counter the Mongols’ love of war.