Dayan Khan in the context of "Altan Khan"

Mongolia is a landlocked country in East Asia. Bordered by Russia to the north and China to the south and southeast, it covers an area of 1,564,116 square kilometres (603,909 square miles), making it the 18th-largest country in the world and the second largest landlocked country after Kazakhstan, as well as the largest landlocked country that does not border an inland sea. With a population of 3.5 million, it is the world's most sparsely populated sovereign state. The country constitutes a significant portion of the Mongolian Plateau, and its natural environment is characterized by grassy steppe, mountains to the north and west, and the Gobi Desert to the south. Ulaanbaatar, the capital and largest city, is home to roughly half of the country's population.

The territory of modern-day Mongolia has been ruled by various nomadic empires, including the Xiongnu, the Xianbei, the Rouran, the First Turkic Khaganate, the Second Turkic Khaganate, the Uyghur Khaganate and others. In 1206, Genghis Khan founded the Mongol Empire, which became the largest contiguous land empire in history. His grandson Kublai Khan conquered China proper and established the Yuan dynasty. After the collapse of the Yuan, the Mongols retreated to Mongolia and resumed their earlier pattern of factional conflict, except during the era of Dayan Khan and Tumen Zasagt Khan.

The Northern Yuan was a dynastic state ruled by the Mongol Borjigin clan based in the Mongolian Plateau. It existed as a rump state after the collapse of the Yuan dynasty in 1368 and lasted until its conquest by the Jurchen-led Later Jin dynasty in 1635. The Northern Yuan dynasty began with the retreat of the Yuan imperial court led by Toghon Temür (Emperor Huizong of Yuan) to the Mongolian steppe. This period featured factional struggles and the often only nominal role of the Great Khan.

Dayan Khan and Mandukhai Khatun reunited most Mongol tribes in the late 15th century. However, the former's distribution of his empire among his sons and relatives as fiefs caused the decentralization of the imperial rule. Despite this decentralization, a remarkable concord continued within the Dayan Khanid aristocracy, and intra-Chinggisid civil war remained unknown until the reign of Ligdan Khan (1604–1634), who saw much of his power weakened in his quarrels with the Mongol tribes and was defeated by the Later Jin dynasty. The last sixty years of this period featured the intensive penetration of Tibetan Buddhism into Mongol society.

The Chahars (Khalkha Mongolian: Цахар, Tsahar; simplified Chinese: 察哈尔部; traditional Chinese: 察哈爾部) are a subgroup of Mongols that speak Chakhar Mongolian and predominantly live in southeastern Inner Mongolia, China.

The Chahars were originally one of estates of Kublai Khan located around Jingzhao (now Xi'an). They moved from Shaanxi to southeastern region controlled by the Northern Yuan dynasty based in the Mongolian Plateau in the 15th century. The Chahar became a tumen of six tumen Mongols under Dayan Khan and were led by his successors, thus becoming personal appanage of the Northern Yuan monarchs.

Abtai Sain Khan (Mongolian: ᠠᠪᠲᠠᠶ ᠢᠰᠠᠶᠢᠨ ᠬᠠᠨ Абтай сайн хан; 1554–1588) – alternately Abatai or Avtai (Mongolian: Автай хан, meaning who have the gift of witchcraft (Автай) and good (сайн) – was a Khalkha-Mongolian prince who was named by the 3rd Dalai Lama as first khan of the Tüsheet Khanate in 1587. He zealously propagated Tibetan Buddhism among the Khalkha Mongols and founded the Buddhist monastery of Erdene Zuu in 1585.

Abtai was born in 1554 to the Khalkha Mongol prince Onokhui üizen Noyan (b. 1534). He was the eldest among Onokhui üizen Noyan's five sons which include Abugho, Tarni, Tumengken, and Barai. He was the great-grandson of Batu Mongke Dayan Khan (1464–1517 / 1543) and grandson of Gersenji (1513–1549). Blood smeared on his fingers at birth presaged a great warrior and from 1567 to 1580 Abtai led several campaigns against western Oirat Mongol tribes, finally defeating the Oirats' Khoshut tribe at Köbkör Keriye in the mid-1580s. Abtai then placed his son Shubuudai on the Oirat throne. His ferociousness in battle earned him the moniker The Mad Hero or the Mad Taiji of North Khalkha.

The Khalkha (/ˈkælkə, ˈkɑːlkə/; Mongolian: Халх ᠬᠠᠯᠬ᠎ᠠ [ˈχa̠ɬχ]) have been the largest subgroup of the Mongols in modern Mongolia since the 15th century. The Khalkha, together with Chahars, Ordos and Tumed, were directly ruled by Borjigin khans until the 20th century. In contrast, the Oirats were ruled by Dzungar nobles and the Khorchins were ruled by Qasar's descendants.

The two original major Khalkha groups were ruled by the direct male line descendants of Dayan Khan. The Baarin, Khongirad, Jaruud, Bayaud and the O'zeed (Ujeed) became the subjects of Dayan Khan's fifth son Achibolod. They formed the Southern Five Halhs.