This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Kublai Khan, the Mongol prince who would go on to found China's Yuan dynasty, invited the Sakya school hierarch Drogon Chogyal Phagpa to his court and, beginning in 1260, named him Imperial Preceptor. The appointment opened a formal priest patron relationship between the Mongol state and Tibetan Buddhism that historians describe as Buddhism's second introduction among the Mongols, the first having left little lasting trace generations earlier.
Sakya lamas grew steadily influential at the Yuan court in the years that followed, and by 1271, when Kublai Khan formally proclaimed the Yuan dynasty, Buddhism had taken on the character of a de facto state religion across his realm. That standing, however, belonged chiefly to the court itself. The wider Mongol population outside it remained largely untouched by the new patronage, a broader popular conversion that would not arrive until three centuries later.
What this changed for Buddhism's spread was the creation, at the very top of Mongol power, of an institutional bond between the Mongol state and the Sakya school that later Mongol rulers and later schools of Tibetan Buddhism would inherit and build on. The court had adopted Buddhism, ordinary Mongols had not yet, a gap the tradition's later second conversion would go on to close.