From Hovd Travel in Mongolia
The Oirats
The Oirats were originally a forest people who dwelt in the mixed steppe woodlands west of Lake Baikal, around Lake Khuvsgul to the south, and the upper tributaries of the Yenisei River farther west. Their name might be based on the Mongolian word "Oi" (Ой) which menas "forest" or "woods". The Oirats were first mentioned in the "History of the Yuan Dynasty", and a 13th century Persian historian refers to the Oirats by name and said they lived in the basins of the eight rivers which combine to form the Yenisei. They were also mentioned in the The Secret History of the Mongols. In 1204 the Oirats fought against Chinggis Khaan and failed, in 1208 they submitted. From 1260-1264 they fought against Chinggis's grandson Khubilai, who founded the Yuan Dynasty. This also failed, and the Oirats remained subordinate until the fall of the Yuan Dynasty in China in 1368.
By the start of the 15th century the Oirats began to gain power while the Khalkh (or Chinggisid) Mongols in the east were entering their decline. In 1434 the Oirat chieftain Toghan melded the four main Oirat tribes, the Torguud (Торгууд), Durvud (Дөрвөд), Khoshot (Хошууд), and Choros (Чорос), into the first Oirat Empire, which included much of present-day Mongolia, as well as parts of Russia, Kazakhstan, and China. In 1449 Toghan's son Esen defeated a Chinese Ming Dynasty army, took the Ming Emperor Yingzong prisoner, and nearly restored a Mongolian Dynasty on the Chinese throne for the second time in less than 100 years. By the 1490's the Khalkh Mongols had begun to swing the balance of power back in their favor. Queen Mandukhai, one of Mongolia's warrior queens (the other is Galdan's wife Anu) and the widow of Mandagul, the 27th successor to Chinggis Khaan, overthrew the Oirat supremacy and established the Khalkhs as the powerholders once again. In the 1550's the Khalkh Mongols, under Altan Khaan, pushed the Oirats northward into Siberia, and also westward into what is now Xinjiang province in China.
Around 1600 a new Oirat leader named Khara-Khula of the Choros tribe rose to power. In 1606 he convinced the other three Oirat tribes (Torguud, Durvud, and Khoshot) to accept his leadership.
