Jochi's mother, Börte, was born into the Onggirat tribe, who lived along the Greater Khingan mountain range south of the Ergüne river, in modern-day Inner Mongolia.

[5] By forming alliances with notable steppe leaders, such as his friend Jamukha and his father's former ally Toghrul, and with the help of his charisma, Temüjin began to attract followers and gain power.

[14] While Temüjin always regarded Jochi as his son by blood and treated him accordingly, many Mongols, such as his younger brother Chagatai, viewed him as a bastard sired by Chilger-Bökö.

[23] As expected for a firstborn, Jochi received the territories furthest away from the homeland for his ulus (domain): they were located in western Mongolia along the River Irtysh.

[24] This allocation was made with the expectation that Jochi would expand his domains, and so in 1207–08 he campaigned against and subjugated the Hoi-yin Irgen [ja], a collection of tribes on the edge of the Siberian taiga between the Angara and Irtysh rivers.

[25] Jochi secured a marriage alliance with the Oirats, whose leader Qutuqa Beki guided the Mongols to the Yenisei Kyrgyz and other Hoi-yin Irgen.

[27] Jochi would campaign intermittently against the Merkits and their Qangli allies for the next decade, finally destroying the last remnants of the people in 1217 or 1218 alongside Subutai.

The Mongols marched southwards from Genghis's campaign headquarters in modern Inner Mongolia in November 1211: first they attacked the cities in the area between Hohhot and Datong, and then they followed the Taihang Mountains into Shanxi, where they pillaged and plundered in autumn 1213.

[32] In 1218, Genghis was provoked into launching a campaign against the Central Asian Khwarazmian Empire after a Mongol trade caravan was killed by the governor of the border town of Otrar and subsequent diplomatic overtures failed.

Though Genghis appears not to have cared about Jochi's possible illegitimacy, Chagatai vehemently objected to his brother becoming the next khan, shouting "How can we let ourselves be ruled by this Merkit bastard?"

Leaving Chagatai and Ögedei to besiege the town, Genghis took their younger brother Tolui and traversed the Kyzyl Kum desert to attack the city of Bukhara.

What is certain is that the siege was lengthy, lasting between four and seven months, and that it was exceptionally fierce: the defiant Khwarazmian defenders forced the Mongol army to engage in bitter house-by-house urban warfare, with much of the city destroyed either by burning naphtha or flooding from collapsed dams.

[41] Atwood argues that this narrative was a later invention designed to buttress Ögedei's rule as khan of the empire and that Jochi in reality retained primacy throughout the siege.

[43] Genghis likely considered it a military failure on account of its length and destruction; Jochi also erred by not sending his father his rightful share of the loot.

[44] After its conclusion, Chagatai and Ögedei departed southwards to join their father in his pursuit of the renegade Khwarazmian prince Jalal al-Din, while Jochi moved north, ostensibly to bring the Qangli to heel in his new territories, which included the steppes west of the river Chu.

[52] Although a large mausoleum in Ulytau Region in Kazakhstan has traditionally been identified as the resting place of Jochi's remains, radiocarbon dating indicates that it was built much later and that it is not the site of the grave.