Oirats, Oyirads or Ölöds is a common designation for Western Mongol tribes. During the Yuan period 元 (1279-1368) they were called in Chinese Woyila 斡亦剌, Weilate 衛拉特 or 衛啦特, during the Ming period 明 (1368-1644) they were known as Wala 瓦剌, and the Qing 清 (1644-1911) called them Elute Menggu 厄魯特蒙古 or Weilate 衛拉特. In later times the Oirat tribes that had migrated father to the west were given the name Kalmyks.
Lee (2016) suggests to regards the Oirats not as a Mongol people but as a federation of its own right that attempted to replace the Chinggisid Mongols as rulers of the northern steppe, just as the Xianbei 鮮卑 had replaced the Xiongnu 匈奴 and the Uyghurs the Gök Türks. The Manchu intervention ended these attempts.
The Oirats are said to have originally settled in the upper course of River Yenissej, from where they, in the 13th century, migrated southwards and began occupying the slopes of the Altai Range and the upper course of the River Selenga. The whole people was divided into four larger groups in households counted according to military needs. The names of the various tribes differ from source to source, some are ancient Mongolian terms, and even Türkic names are to be found in the listings. In the 14th century Mengke Temür 猛哥帖木兒 emerged as a leader in the wars against the Tatars 韃靼, remnants of the once all-powerful Mongolian federation.
The Ming Emperor Chengzu 明成祖 (r. 1402-1424) dispatched an envoy to confirm the khan in his position. In 1408 khan Maḥmūd 馬哈木 (Batula čingsang) presented tribute horses to the Ming court. He was granted the title of Prince Shunning 順寧王, while other khans of the Oirats were granted similar honours (Prince Xianyi 賢義王 and Prince Anle 安樂王). The Oirats often contended with the Tatars over the control of pastures and the title of khan. In 1410 Emperor Chengzu undertook a military campaign to contain the Tatars. The Oirats used the declining power of the Tatars and occupied territories more to the southeast, formerly used as pastures by the Tatars. In 1414 they even attacked border villages of the Ming empire, so that Emperor Chengzu undertook a punitive campaign to the banks of River Tula. A year later Mahmud begged for pardon and presented the requested regular tribute horses. He died soon and was succeeded by Toγon (Tuoguan 脫懽) as highest leader of the Oirat federation.
In 1434 Tuoguan killed Aruγtai (Alutai 阿魯臺), khan of the Tatars, and the princes Xianyi and Anle. He made a descendant of the Mongol emperors, Toγto Buqa (Tuotuo Buhua 脫脫不花), great khan of the Tatars and himself occupied the office of the great khan's counsellor. Tuoguan died in 1434 and was succeeded by his son Esen 也先. In 1434 Esen Khan felt strong enough to attack the Ming empire. Urged by his courtiers, Emperor Yingzong 明英宗 (r. 1435-1449) headed the Ming army, but he was defeated at Tumu 土木堡 and was captured. The troops of Esen Khan even endangered the capital, but general Yu Qian 于謙 was able to repel their invasion. Esen Khan accepted to conclude peace and sent back Emperor Yingzong. Toghto Bukha, the actual great khan, thereupon criticized Esen Khan for his ventures, and was killed by the latter. Esen Khan, now official great khan of the Oirats, became ever more arrogant and was finally assassinated in 1455. The real power of the Oirats from then on declined, but they continued exerting control over the city states along the Silk Road and sometimes even invaded territory of the Ming empire in the province of Gansu. Part of the Oirats also migrated to Qinghai and Gansu.
Around 1600 the various tribes of the Oirats underwent a restructuring, merged with Türkic peoples in its neighbourhood, and four larger federations emerged, namely the Dzungars (Jegün γar) 準噶爾, Dörbed (Durbote 杜爾伯特), Qošod (Heshuote 和碩特, Khoshot) and Torgud (Turhute 土爾扈特), and the smaller tribe of the Huite 輝特 which used the same grassing grounds as the Turkhut. The Dzungars were also known as Čoros (Chuoluosi 綽羅斯) because their chieftains were related to the leaders of the Durbot which came from that family. The are in which these four larger tribes pastured their cattle reached from Kirgistan in the west to the Qinghai heights in the east.
The Dzungars first settled on the middle course of River Erqisi and later moved to the valley of River Ili; the Durbot settled on the banks of River Erqisi; the Turhut settled in the region of Tarbahatai and later moved westwards; the Khoshot roamed the region between River Emin and Ulumuqi. The tribes normally wandered around as pastoral nomads and only met during the so-called kyurgan 丘爾干 meetings where larger political issued were debated and ties confirmed. In the beginnings the leader of all Oirats were princes of the Khoshot tribes of which the names Bobei Mirza 博貝密爾咱, Haninuoyan Hongguor 哈尼諾顏洪果爾 and Baibagas 拜巴噶斯 are known. After 1620 the power shifted towards the Dzungars, and the leading chieftains from then on were Qara qula (Halahula 哈剌忽喇) and his son Erdeni Ba’atur Hung Tayiji 巴圖爾琿臺吉. In 1640 the Oirats and the Khalkha Mongols met at Tarbahatai, fixed a new common law code for the two federations, and decided that Tibetan Buddhism was to be the common religion of all Mongol tribes. The Uighur-Mongolian script that had hitherto been used to write texts of all Western Mongol tribes, was in 1648 replaced by the Tangut script, i. e. the Tibetan script.
In 1628 the Turkhut, the Erlek 額爾勒克 and part of the Khoshot and Durbot migrated towards the lower course of the River Ejile (moder River Furga, Russia). Ten years later they returned towards the east. Their leader, Güshi or Gušri Khan 顧實汗, lead them towards Qinghai. With the pretext of pretecting the Yellow Hat School of Tibetan Buddhism they occupied Qinghai and the Tibetan plateau. In the meantime, the remaining parts of these tribes, which had remained north of the Tianshan Range 天山, became part of the Oirat federation. This federation was lead by the Dzungars and was therefore by the Qing government called "the Dzungars".
In the 1670s Galdan 噶爾丹 emerged as the great khan of the Dzungars. He controlled all the region north and south of the Tianshan Range and was even able to exert control on Kashgar and Samarkand. His successors Tsewang Arabdan 測妄阿拉布坦 and Galdan Tsering 噶爾丹策零 reorganised the tribes into a military machine that challenged the Qing empire as well as Russia. After Galdan Tsering's death in 1745 the federation disintegrated. From 1755 on the Qing court undertook a large campaign to supress the last khan of the Dzungars, Amursana 阿睦爾撒納. In 1772 the Turkhut under their khan Ubaši (Wobaxi 渥巴錫) migrated towards the east and were, just like the Dzungars earlier, integrated into the banner-league system used by the Eastern Mongols. They so became part of the Qing empire. Their chieftains were appointed commanders-general (zuoling 佐領, or jassak 札薩克) of their peoples. The descendants of the Oirat still live in the modern regions of Qinghai, Gansu, Xinjiang and Inner Mongolia.