Esen taishi Esen taishi ( ; died 1455 ) was a powerful Oirat Khagan of the Northern Yuan Dynasty in Mongolia in the 15th century . He is best known for capturing the Zhengtong Emperor of the Ming Dynasty in 1450 after the Battle of Tumu Fortress and briefly reuniting the Mongols . The Western Mongols reached their peak under his rule . Youth and early career . Esen was born to his father , Toghon , the Choros taishi ( grand preceptor , from 太師 ) who had expanded Oirat territory substantially , with more Mongol tribes acknowledging his supremacy . His early campaigns were against the Chaghatayid khans of Moghulistan . Esen three times defeated and twice captured the Moghul i ruler Uvais ( Ways Khan ) ( 1418 – 1432 ) . Esen released him respecting his Chinggisid blood in both cases . The second time Uvais granted Esen his sister Makhtum Khanim who bore his two sons . Esen had to nominally convert to Islam in order to marry the Muslim princess , but remained effectively a shamanist . After his father died in 1438 , Esen inherited his position , taishi , for the reigning khan Togtoo - Bukha ( r . 1433 - 52 ) . Under Esen taishi ' s leadership , the western Mongols and other Mongol tribes who support Togtoo - Bukha conquered the rest of Mongolia , and received the submission of the Jurchens and the Tuvans ( Uriankhais ) in Manchuria and Eastern Siberia . It is unarguably true that the Oirat warriors played a crucial role in this conquest . In the 1430s Esen also took over control of the Mongol kingdom called Qara Del in Hami oasis on the Silk Road between the Gobi and the Takla Makan deserts ; after 1443 - 45 his conquest reached the northern border of Korea . Conflict with the Ming . Esen ' s policy irritated or threatened the Chinese Ming Dynasty . The Ming had for some time pursued a " divide and rule " strategy in dealings with their northern neighbors , maintaining trade and tribute relationships , functioning as a kind of state - subsidized monopoly , with multiple leaders who they could then turn against one another by inciting jealousy or suggesting intrigue . A unified Mongolia under one ruler was , however , much less susceptible to such tactics . Also , many of the tribes brought under Oirat dominion by conquest either had inhabited areas claimed by China already , and other tribes had been pushed south into Chinese territory seeking to escape Oirat subjugation . The Chagatayid Hami oasis , furthermore , had paid tribute to the emperor before Esen convinced its ruler that bounty should go to the Oirat instead . Throughout the 1440s , Esen increased both the frequency of tribute missions to China and the number of representatives sent on each mission , meaning that the Chinese were obliged to provide ever - more expensive hospitality to the Mongols , irrespective of the actual trade or tribute being negotiated , and , according to surviving Chinese accounts , the Oirat demanded more and more lucrative tribute and trade agreements further skewed in the Mongols ' favor . One Chinese tactic for dealing with the situation , provoking rivalry between Mongol leaders , failed completely as they underestimated the degree of power Esen wielded and chose " rivals " too far below him in status for the strategy to be effective , including the figurehead Khan Togtoo Bukha . In addition , their other main tactic , meeting each demand for increased tribute or trade value with a decrease , backfired as well . Esen encouraged hundreds of Mongol , Hami , and Samarkand based Muslim merchants to accompany his missions to the Ming Emperor . Since 1439 the Emperor Togtoo Bukha and Esen had been sending envoys to China , often numbering more than 1 , 000 . In response to this inflation of numbers , the Zhengtong Emperor ( 1427 – 64 ) decreased the gifts to Esen and Togtaa - Bukha Khaan and closed border - trade with the Mongols . Invasion of Ming China . In retaliation for real and perceived slights , Esen Tayisi led an Oirat invasion of northern China in 1449 which culminated in the capture of the Zhengtong Emperor at Tumu . The large - scale , three - pronged invasion began in July , with Khan Togtoo - Bukha leading the easternmost force to Liaodong , the grand councillor Alag attacking Xuanfu , and Esen himself heading the troops that sacked the city of Datong in August . Another column of the Mongols invaded Ganzhou . Acting on extremely poor advice from one of his advisors , the emperor also chose to lead his own armies into battle , with disastrous consequences . Initial Chinese failures . The campaign was a series of routs and massacres of Chinese forces at Oirat hands , even though the imperial troops in the region are estimated to have numbered as many as 500 , 000 and Esen Tayisi had brought only 20 , 000 cavalry , expecting mainly to engage in traditional Oirat border raiding . Datong lay north of the Great Wall of China , and thus beyond its protection . After the initial attack on Datong , Esen feinted back to the Mongolian steppes . The emperor and his hastily - raised army chased the invaders west and met an ambush upon arriving at Datong . The Oirat horsemen harried the Chinese retreat back towards the wall for four days , through terrific thunderstorms , until the imperial army reached Tumu Bao ( often translated Tumu Fortress ) . But rather than having secured a defensible position , the Chinese were trapped against the north side of Tumu , and Esen annihilated the Chinese army sent against him . Capture of the Ming emperor . Most of the remaining soldiers , as well as all officers and courtiers of rank except the emperor himself , were slaughtered . Esen was still some distance away , near Xianfu . Six weeks later , when the captured emperor was brought to his camp and he had brought a more substantial force to the vicinity of Beijing , Esen attempted to ransom the emperor back to the Chinese . According to some accounts , it was at this point that Esen was granted the title " Tayisi " . In any case , the Chinese refused to negotiate a ransom , perhaps in part because the emperor ' s brother ( a prince variously referred to as Zhu Qiyu , later the Jingtai Emperor ) was by then installed on the throne and not eager to give up his new position . Yu Qian , the defence minister of Ming , who was organizing Chinese resistance , commented that the emperor ' s life is not as important as the fate of the country ; he also believed that ransoming the emperor might boost the Mongols ' morale and reduce that of the Ming . Laying siege to Beijing . His ransom demand rebuffed , whether because the Chinese were calling Esen ' s bluff , believing he would consider the emperor more valuable alive than dead even without the possibility of ransom , or because the acting emperor was content not to obtain his brother ' s freedom , Esen began laying siege to the city . Esen offered the Emperor his sister in marriage , but the Emperor refused . The disheartened garrison in Beijing was under the command of the new commander Yu Qian who soon turned this unfavourable situation into a positive one . Not only did he use Beijing ' s fortifications to his advantage , but he also deployed various schemes to destroy the morale of the Mongol army . At one point , he ordered his forces to pretend that they had lost control of the city gate in order to lure a large force of Mongol riders into the city . Once a portion of the Mongol force was inside , the gate was shut and the Mongols were ambushed . Esen ' s sworn brother ( anda ) was killed in the attack . Having failed to take the city , Esen was soon forced to retreat under pressure from his own troops and by the arrival of reinforcements from elsewhere in China . Negotiations . The Ming court elevated the Jingtai Emperor ( r . 1449 - 57 ) to the throne . Esen sent the captured emperor back in 1450 . Since the Mongols relied on their trade - and - tribute relationship with China , Esen was then obligated to reopen negotiations from a much weakened position . While Sino - Mongol trade did not cease entirely during the Tumu Crisis , as the incident has come to be called , Esen had not only failed to win better terms than the prior arrangements , he was forced to accept less favorable terms in return for resumption of more normal relations with the Ming Empire . But Esen and Togtoo - Bukha again invaded the north of China , devastating the area around the confluence of the Nen and Songhua rivers . Reign and death . Although , Togtoo - Bukha opposed Esen ' s policy of confrontation with the Ming , there was not any serious tension between the two . They quarreled over the designation of the heir of the throne . Esen wanted a son of his sister who was the wife of the khagan to be the successor of Togtaa - Bukha . But Togtoo - Bukha nominated his another son of the eastern Mongolian khatun as his heir instead . Togtoo - Bukha supported the Three guards and led his own forces openly against Esen in 1451 ; but they were outnumbered by Oirat loyalists and the nominal Khan was caught and killed by eastern tribesmen as he attempted to retreat . Togtaa - Bukha ' s brother Agbarjin jinong ( viceroy ) , who married Esen ' s daughter Tsetseg , deserted to the Oirats and was promised the title of khagan of the Northern Yuan Dynasty . However , Esen murdered him after he invited Agbarjin with his male relatives at the feast . Esen attempted to kill the baby son of her daughter by Agbarjin ' son , Qara Qurtsaq , but she and Esen ' s grandmother , Samur , hid the infant prince , Batu - Mongke , who would be a direct ancestor of Dayan Khan . Within eighteen months of his defeat of the titular Khan Toghto - Bukha , in 1453 , Esen himself took the title of Great Khan of the Great Yuan ( 大元天盛可汗 ) . At the same time the Oirats began an expedition into Moghulistan , Tashkent , Transoxiana The Ming emperor was among the first to acknowledge the new title , but the reaction of Esen ' s fellow Mongols , Oirat and otherwise , mostly ranged from disapproving to enraged . Though Esen ' s line was related to the royal line descended from Temüjin ( Genghis Khan ) through his grandmother Samur gunji ( princess ) , it was unlikely that he would have been considered eligible for election as Khan , and in any case Esen ignored the usual selection process : rather than the title of khan falling automatically to the eldest eligible male of the line , as in primogeniture , Mongol leaders were traditionally chosen by means of the kurultai , an elective monarchy system , with the members of a lineage voting to choose the title ' s successor from among themselves . This dissatisfaction soon escalated into open revolt against Esen ' s leadership . Esen gave his son Amasanj the title of taishi , an action that led his powerful general Alag , who had expected to receive the title himself , into rebellion . Notable Oirat leaders joined the rebellion against Esen who was defeated at the battle and murdered in 1455 , the year following his assumption of the title of khan , by the son of a political opponent whom Esen had executed . After his death , the Oirat no longer held sway over the areas of Mongolia which had come under their control only under his rule , and remained divided among themselves for many years . The 17th and 18th century Zunghar rulers considered themselves to be descendants of Esen Taishi . References . Twitchett , Denis , Frederick W . Mote , & John K . Fairbank ( eds . ) ( 1998 ) . " The Cambridge History of China : Volume 8 , the Ming Dynasty , Part 2 , 1368 - 1644 " . Cambridge University Press . pp . 233 – 239 . ISBN 0 - 521 - 24333 - 5 . Google Print . Retrieved 2 November 2005 . Mancini , Robert David ( publication year unknown ) . " Dharma Daishi , Great Teacher of Buddhism and the Martial Arts " . van der Kuijp , Leonard W . J . ( 1993 ) . " Jambhala : an imperial envoy to Tibet during the late Yuan " . " The Journal of the American Oriental Society " 113 ( 4 ) , 538 – ?