Ming were indeed too weak to strike into the Mongol heartland like the deceased Yongle Emperor had done in the past. Ming showed its disapproval by calling Taisun Khan of the Northern Yuan instead of Taizong (太宗) of the Great Yuan. After Toghan died, Taisun Khan made Toghan's son Esen Taishi a taishi, and his younger brother Agbarjin a jinong. During the reign of Taisun Khan, Esen Taishi subjugated the Jurchens in Manchuria, the Kara Del kingdom around Hami City, and the Uriankhais (Tuvans) in Siberia. Conflict with Ming dynasty Despite his ambitions, Taisun Khan was still far more inclined towards peaceful relations with the Ming dynasty than his commander Esen. He kept a friendly relationship with the Ming court. His taishi, Esen, was even more ambitious and wanted to restore the glory of the Mongol Empire in name and territory. Esen first directed his attention to the Hami Oasis where the Ming ally, Borjigin prince descended from Chagatai Khan, ruled. Repeated raids and threats by Esen forced him to surrender in 1448. Esen then attacked the Gansu region where the Mongol satellite states of the Ming, known collectively as the Three Guards, were located. The Fuyu guard was forced to flee, and Esen appointed his own governor in the area. Taisun Khan personally led the attack on the Taining guard. After that, Esen also plundered the Doyin Uriankhai guard, forcing them to surrender. With the submission of the Three Guards, the revived Yuan dynasty became a direct threat to Ming. When the Ming refused the Mongols their request to allow additional Mongol envoys to China and a Chinese princess, Esen decided to invade the Ming. Taisun Khan was apprehensive of this and did not support Esen at first. However, he was induced to lead the easternmost force of Uriankhais to Liaodong in 1449. He besieged the city and ravaged its outskirts for 40 days while Esen crushed the Ming armies en route to Beijing. After defeating the Ming army during the Tumu Crisis and capturing the Zhengtong Emperor the Mongols returned north. Taisun Khan treated the captured emperor kindly. Upon realizing that the Ming would not pay a ransom for the captured emperor, the Zhengtong Emperor was returned in 1450. Decline Taisun Khan's consort, the elder sister of Esen, attempted to persuade the khan to make his sister's son the designated heir. The request was denied, causing Taisun and