The Yuan dynasty was a Mongol-led imperial Chinese dynasty. During its existence, its territory was divided into the Central Region (腹裏) governed by the Central Secretariat (Zhongshu Sheng) and places under control of various provinces (行省) or Branch Secretariats (行中書省), as well as the region under the Bureau of Buddhist and Tibetan Affairs (Xuanzheng Yuan). In addition, the Yuan emperors held nominal suzerainty over the western Mongol khanates, but in reality none of them were governed by the Yuan dynasty due to the division of the Mongol Empire.