Smaller military operations of the Mongol Empire in Central Asia included the destruction of surviving Merkit and Naimans (which involved forays into Cumania) and the conquest of Qara Khitai.

Expansion into Central Asia began in 1209 as Genghis Khan sent an expedition to pursue rivals who had fled to the region and threatened his new empire.

[2] The Uyghur kingdom Qocho and leaders of the Karluks submitted voluntarily to the Mongol Empire and married into the imperial family.

[3] In either late 1208 or early 1209, as part of the conquest of Siberia, a Mongol expedition commanded by Genghis Khan's oldest son, Jochi, met the Merkits and Naimans at a branch of the Irtysh.

[12][13][14][15] To solidify the alliance, Al Altun, the youngest daughter of Genghis Khan and his chief consort Börte, was married to Barchuq.

[citation needed] In 1211, the Karluks, a Turkic confederation the area of the southern Ili, in the Tarbagatai Mountains and northern Xinjiang, also voluntarily submitted to the Mongols.

Because the Karluks submitted voluntarily like the Uyghur, their military was allowed to operate as an auxiliary without integrating into the main, atomized army.

[7] The independent nomadic tribes that the Mongols had encountered in Central Asia and Eastern Europe may have been at least part of the impetus for Ögedei Khan to launch a western campaign in 1235.

In 1124 some Khitans moved westward under Yeh-lü Ta-shih’s leadership and created the Qara Khitai Khanate (Western Liao) between in the Semirechye and the Chu River.

However, their power was shattered in 1211 through the combined actions of the Khwārezm-Shah ʿAlāʾ ad-Dīn Muḥammad (1200–20), and Küchlüg, a fugitive Naiman prince in flight from Genghis Khan’s Mongols.

The Mongol invasion of Central Asia however would entail the utter destruction of the Khwarezmid Empire along with the massacre of much of the civilian population of the region.

According to Juvaini, the Mongols ordered only one round of slaughter in Khwarezm and Transoxiana, but systematically exterminated a particularly large portion of the people of the cities of Khorasan.