Esen Taishi

Esen (Mongolian: Эсэн; Mongol script: ᠡᠰᠡᠨ; Chinese: 也先; d. 1455) was a powerful Oirat taishi and khagan of the Northern Yuan dynasty between 1453 and 1454.

Esen, the son of Oirat taishi Toghon, distinguished himself in wars against Moghulistan, twice capturing its khan. After his father's death in 1438, he became the de facto ruler of the Mongols, despite being formally subordinate to Taisun Khan of the Northern Yuan. During the 1440s, he seized Hami on the Silk Road, controlled Gansu's Mongol principalities, subdued the Uriankhai, and unified Mongolia.

His relations with Ming China were marked by restricted trade and rising tensions. The Ming limited exchanges to tribute, and in 1449, reduced the goods granted to Esen's envoys. This led to war, partly due to the Ming refusal to grant an imperial princess to Esen's son. In July 1449, Esen led a major invasion of China. Ming forces under Emperor Yingzong were decisively defeated at the Battle of Tumu Fortress, and the Emperor was captured. As a result, the Ming enthroned his brother, the Jingtai Emperor, and Esen was unable to capitalize on his victory, making peace in 1450 and releasing Yingzong.

In the early 1450s, Esen eliminated Taisun during a succession conflict, briefly installed and killed a puppet khan, and then proclaimed himself khan. His later designation of his son, Amasanj, as the taishi provoked a rebellion led by his subordinate Alag, in which Esen was defeated and soon killed.

Esen was the son of the Oirat taishi, Toghon, of the Choros clan. His military abilities were evident during his father lifetime. In the 1420s, he led three successful campaigns against Eastern Moghulistan, capturing its ruler Uwais Khan twice. During this time, he also expanded Oirat influence to Beshbalik. In the 1430s, Esen accompanied his father in campaigns against the Khalkha taishi Arughtai, resulting in Arughtai's death in 1434. This victory allowed Toghon to install his own candidate, Taisun, as a puppet Great Khan of the Northern Yuan. To solidify this alliance, Taisun was married to Esen's elder sister. Toghon himself held the title of taishi (also known as taiji), derived from the Chinese term taishi (太師), meaning "grand preceptor" or "heir apparent." Among the Mongols, this title was considered the highest rank below that of khan, a position that Toghon could not attain as he was not from the lineage of Genghis Khan. In European languages, the title taishi is often translated as "chief" or "prime minister".

After Toghon's death in 1438, Esen inherited his title of taishi and began pressuring the "guards" (wei) along the northwestern frontier of Ming China. In 1443, three thousand Oirats attacked Hami, an important oasis that acknowledged Ming suzerainty, and captured the local prince's mother and wife. Esen attempted to persuade the prince to visit the Oirat camp and accept their overlordship, but the prince refused. The Ming court strongly protested against the Oirat raid, and Esen, not wanting to challenge China at that time, eventually released the noble captives. In 1445, he once again attacked Hami and captured the prince's mother and wife, inviting him to visit. Despite assuring the Ming authorities that he would not give in to Esen's demands, the prince of Hami eventually traveled to Oirat territory in 1448 and remained there for an extended period as a member of the Oirat leader's retinue.

In 1443, Esen attempted to compel the leaders of the Mongol tribes of Shazhou and Qizhin guards in western Gansu to form an alliance through intermarriage. Negotiations were delayed as the leaders sought support from the court in Beijing, warning them of Esen's intentions. Despite this warning, the Ming authorities took no action, which only encouraged Esen to continue with his plans. In 1445, he forced the leaders of Shazhou and Qizhin to accept Mongol titles and established a "provincial government of Gansu" solidifying his intention to take control of the region. The following year, in 1446, the majority of the Shazhou tribe was intimidated and chose to flee. Most of them sought refuge in China, while a small number joined Esen. On the other hand, the Qizhin tribe remained in their territory despite the threat from the Oirats. They repeatedly requested permission to abandon their land and seek refuge in China, but Emperor Yingzong of Ming rejected their appeals. He assured them that if they "kept a watchful eye on the situation in the west and in case of an impending invasion warned the Ming generals [they] would receive help in time and be quite safe". In order to persuade them to stay, the Emperor also provided them with necessary supplies such as grain. As a result, the majority of the Qizhin tribe remained in their territory until 1454, when Esen once again attempted to force them into an alliance.

Esen pursued an aggressive policy in the northeast, forming an alliance with three Uriankhai guards—Daning, Duoyan, and Fuyu—in the early 1440s. This alliance was solidified through his marriage to the daughter of the chieftain of one of these guards, Daning. These Uriankhai guards served as spies for Esen within China. However, when the Ming launched a punitive expedition against the Uriankhai in 1444 due to repeated raids, Esen did not provide assistance and instead took advantage of their weakened state to plunder their territory. By 1447, Esen had conquered the Daning and Duoyan guards and forced the Fuyu to migrate. This final act of aggression gave Esen control over a vast territory, stretching from present-day Xinjiang to Korea.