Answer:
With the help of military.
Explanation:
The empires in China and Dar al-Islam were able to maintain and justify power by using the military. Those people would ruled on the empire that has a support of military because military has all the power. In the empires of china, generals ruled over the empire due to their influence on the military forces whereas in Dar al-Islam, the military plays a great role in forming a government. So we can say that both empires in China and Dar al-Islam uses military to maintain power.
