What was essential in order to establish an empire in the mountainous terrain?

Strong agricultural and distribution base.

Explanation:

Establishing mountainous terrain gave empires in the past with a  lot of advantages in military's perspective. Since the area is difficult to reach, the mountains acted as natural defense that prevented a lot of enemies from reaching the area.

But, this act as a double edged sword.

It made it very difficult for empires in mountainous terrain to establish trading relationships to outsiders. To fulfill their basic needs, they need to rely on their own agricultural base or invested in the construction of roads that they can use to distribute their products outside the region.

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