He is best known for forming and leading a coalition of the Four Oirats in battle against Ubasi Khun Tayishi, the Khalkha prince who ruled the Altan Khanate in present-day northwest Mongolia.
They were pressured to migrate west to that area from their home in the Altai Mountains by Ubasi Khun Tayishi who was expanding his state by robbing the Oirats of their valuable pastures.
In so doing, Kharkhul's objective was to establish the political and military unity that his ancestor Esen Tayishi once demanded from the Oirat princes and, in the process, forge a new state.
By 1609, Khara Khula won a decisive victory against Ubasi Khun Tayishi, forcing the Altan Khanate to withdraw from Oirat territory in the Kobdo region of present-day northwest Mongolia.
But the unity would soon dissolve after the victory, as some Oirat princes, no longer fearing the Ubasi Khun Tayishi, resumed their traditional nomadic ways, favoring independence over centralization.
As Kharkhul's power and prestige grew from his victories over the Altan Khanate, the Oirat princes felt his dominance over them, particularly the Torghut tribe whose leaders wished to maintain the freedoms they once enjoyed without a central political figure.