How did genghis khan conquer such a large empire

How were Mongols able to conquer such a large empire? By ruthless inter-breeding.

Explanation:

They had traditions of extreme warfare violence followed by murdering the ruling class of the other tribes then interbreeding the two tribes, so the offspring would all be a part of the Mongols one tribe

the award is named for an american naval historian and theorist, rear admiral alfred thayer mahan, united states navy who, through his writing, provided stimulus and guidance to those who share in the defense of the nation.