From 1204 to 1209, Genghis Khan expanded Mongol influence. He sent Jochi north in 1207 to conquer tribes in Siberia, gaining access to valuable resources like grain, furs, and gold by marrying into the Oirats and defeating the Yenisei Kyrgyz. The Mongols also moved west, overcoming a Naiman-Merkit coalition and securing Uyghur allegiance, marking the Mongols' first submission from a settled society.

Genghis began attacking the Western Xia kingdom in 1205, partly to retaliate against their sheltering of Senggum and to boost the Mongol economy through raids. The Xia's weak northern defenses led to Mongol victories, including capturing the fortress of Wulahai in 1207. In 1209, Genghis personally led an invasion, capturing Wulahai again and advancing on the Xia capital. Despite initial setbacks and a failed siege due to inadequate equipment, Genghis managed a tactical retreat that tricked the Xia into a vulnerable position, leading to their defeat.

The siege of the Xia capital stalled due to the Mongols' lack of siege technology, and a failed attempt to flood the city led to a Mongol retreat after the dam broke. Eventually, peace was made with the Xia submitting to Mongol rule in exchange for stopping the attacks, with the Xia emperor sending tribute, including his daughter, to Genghis.